So its one standalone PC that duplicates the username no matter which PC its run on & no matter who is running it?
In that case there must be some form of corruption or other code issues.
Newer versions of Access are (rightly) less forgiving of code errors
You've already compacted with no change
So check the following in turn - apologies if you already know about all of the following
1. First do a backup
2. Do you have "require Variable Declaration" ticked in VBE Options. If not, tick it
As you may know that will add the line 'Option explicit' to all new code modules BUT not to existing ones
So go through and add that as the second line (usually after Option Compare Database) of each code module if it is missing
Now click Debug...Compile & fix each declaration error that is picked up.
Continue until it is fully compiled (the Compile menu item will be disabled)
3. Now try opening again. Is the problem fixed? If not go to step 4
4. Next try decompiling as I suggested
http://www.fmsinc.com/microsoftacces.../decompile.asp.
It only takes a couple of seconds and will fix any compilation errors.
Compile again. Compact
5. Now try opening again. Is the problem fixed? If not go to step 6
6. Create a new blank database. Import all items from the old database into that.
Check there are no missing references. Compact
7. Now try opening again. Is the problem fixed? If not reinstall Access (or just give up!!!!!)
HTH