When processing of your EPG import fails (or your Media Center EPG doesn't appear to be updating as expected) - you should run a 'test' import from the Big Screen EPG Configuration program and observe what information is displayed in the log window (or in the Console window) - so you can better identify what has gone wrong.

Then - if you can see an error being reported (in this console window) - have a look for some of the most commonly reported problems below (as this may offer some further insight as to what is causing it - and what steps you may be able to take to get yourself back up and running).

Problem : You receive an Error Messsage 'Error Generating MXF File : Reference to undeclared entity 'XXXX'. Line XXXX, position XX.' when running an import.

Solution : This error indicates that your source XMLTV file has invalid XML metadata (such as undeclared entities) within it. This is known to occur on XMLTV Feeds which are scraped from HTML sources - such as Digiguide or RadioTimes UK and some others. In order to fix this - you may need to use the BSXFIX command line tool (available from the Big Screen EPG Download Page) to 'clean up' your XMLTV file before it can be imported. This tool can perform the actual HTTP download of the XMLTV file - and then write out the 'fixed' version to your local harddrive - and you'd then configure Big Screen EPG to point to this local file instead of the online HTTP source.
 
As this is a command line tool - you can then add this new 'Action' into your BSEPG Scheduled Task (prior to the bsetool.exe action) - so it always runs just before an import - or you can alternatively add a new scheduled task which runs *before* your Big Screen EPG scheduled task.

Problem : You receive an error message 'Error Importing your MXF File : An Error Occurred while running loadmxf against generated data!'

Solution : This problem indicates there was an issue when importing your generated MXF File (Located in %ProgramData%\Big Screen\EPG\bse-epgdata.mxf) to Media Center.
 
There is a few reasons why this can happen - and you should observe the % failed value to get a better idea of what is happening.

If your loadMXF Failed % is a very low value (ie. <20%) : this can indicate that your MCEPG-*.db database is actually corrupted (for some unknown reason) - and further indication of this is that your 7MC EPG is very slow to load or crashes ehshell.exe (when accessing EPG inside Media Center). Unfortunately - the only known fix for this at this time is to do a MCE DB Reset - and basically start again (which will return you to 'first run' state in Media Center and require you to retune your channels/setup your TV Sources). If that doesn't work you might be required to reinstall Windows 7. Note that if you are doing a MCE DB Reset - your BSEPG configuration /settings file (importsettings.xml) will remain intact - so you shouldn't need to reconfigure BSEPG after a reset (only rerun it once you've setup your channels).

If your loadMXF Failed % is ~80%-90% : This indicates there's actually an issue in the MXF file generated by Big Screen EPG.  At time of writing (v1.0beta) - there are not any known issues/bugs which would cause this problem - and you should report this issue so that it can be addressed/fixed if need be.  (NB: Earlier beta versions of Big Screen EPG had various issues with 'auto correcting' corrupt/invalid XMLTV metadata which should now be fixed).  If you do find errors occurring on specific channels - you can temporarily disable the offending channel from the Big Screen EPG source while you wait for a solution. You should also contact the XMLTV provider person/company/author and notify them of this problem (as it's likely they are publishing some invalid data which can be fixed on their end).

If your loadMXF failed % is ~97% (and may also report message 'mergedLineup.LineupMergeRule is null') : This indicates you've not yet setup your TV sources (or tuned in your channels) - and no 'default channel lineup' exists in Media Center. To fix this you should setup your TV Channels in Media Center TV Setup - and ensure you can at least tune in/ watch live TV. (as you cannot import EPG data with Big Screen EPG until this is done and at least one valid TV Tuner/Source is present).

Problem : No EPG Data appears to be getting imported.

Solution : There are many reasons why this can happen - however the first thing to check is that you are actually getting some valid EPG data coming through from the file. When Big Screen EPG is processing your XMLTV file - it will report the number of programs/series/channels etc it located (which fall within valid date ranges) - as indicated in the log message such as 'channels=389/scheduleentries=149924/programs=123010/series=1335:11111' - this tells you how many entries were found. If any of these figures are '0' (or indicate very low numbers) then that is a telltale sign there is something wrong with your XMLTV source (as a general rule - you should be getting anywhere from 20-300 schedule entries per each channel you have).

Problem : EPG data is not appearing in the Media Center EPG after a successful import / channel logos are not appearing.

Solution : There's a lot of different reasons for this (and deserves a seperate troubleshooting post) - however the first point of call is to make sure your Big Screen EPG Listings have actually been mapped to Tuned channels in Media Center. Please see the Big Screen EPG help file (Installed with Big Screen EPG) and follow the appropriate step by step guides to ensure your channels are actually mapped (and that you aren't in fact looking at EIT/Inband EPG data instead). You can further test this by looking at the EPG data that does come up (if present) and comparing it to the actual epg data in your XMLTV File (ie. checking that descriptions and episode titles are the same).