This is a totally unexpected result of a service pack. Typically service packs are something that are fairly safe, unless they are an “R2” release in the more recent GP2013 and GP2015 versions. But this was GP9, and I was applying Service Pack 4 so I could upgrade them to GP2015 in a few months (GP9 will not directly upgrade to 2015, but you need to add Service Pack 4 to upgrade to 2010 and you can then go to 2015).
I discovered that somehow something got out of SYNC, so I edited the DEX.INI file, and changed SYNCHRONIZE=FALSE to SYNCHRONIZE=TRUE.
I then launched GP Utilities, and low and behold it said “Synchronizing account framework”. I then selected “Synchronize forms and reports dictionary” (normally this says “Upgrade Forms and Reports dictionary”) and clicked process.
Once this was done, I launched GP and ran the GL Trial Balance Detail report again and low and behold the error was gone.
Credit where credit is due, Microsoft KB2492442
Lesson learned: Instead of jumping in to my 10 year knowledge of troubleshooting GP, sometimes it’s best to search Google first and foremost and then dive into my normal troubleshooting steps.