That suggests that you probably have one or more hands where the big blind amount is recorded as zero.
*** Before you do anything else, MAKE A BACKUP OF YOUR DATABASE using File > Backup. ***
Please save the attached .pt4rpt file to your computer and then go to the My Reports tab in PT4.
Click the grey disk icon and choose "Import" - see the attached screenshot.
Select the file that you just saved.
The report will run automatically when it is imported.
This should show you any sessions which have a zero big blind size.
(If the report is empty, please let me know.)
If it lists any sessions, check that you have the original hand history files for those sessions.
By default these will have been moved to the 'Processed' folder, which you can find via File > Open User Data Folder from the PT4 menu, although you may have them archived somewhere else if you imported them into PT4 using 'Get Hands From Disk' rather than while playing.
If you don't have the original hand history files be sure to export the relevant sessions before proceeding. (Database > Export)
REMINDER - BE SURE YOU HAVE A BACKUP OF YOUR DATABASE BEFORE YOU CONTINUE (or at least all of the hand history files)
We will now remove the sessions with the zero blinds, before re-importing them.
From the PT4 menu choose Database > Purge Hands.
Select the sessions listed in the report you just imported (shift-click or control-click to select multiple sessions) and click 'Purge Session(s)'.
This may take a little time if there were many sessions, although hopefully there would only be a small number.
Try the custom which was giving you the error again now - be sure to click 'Refresh'.
Does it display OK now?
If not, let me know.
If the custom report works now, try re-importing the affected sessions from the original (or exported) hand histories, using 'Get Hands From Disk'.
If that re-introduces the problem, attach the hand history files you imported to a
Support Ticket with a link to this thread so that I can investigate.