I use KeePassDroid, and I opened the exact same file on GD from my phone since every time I close it after adding an entry on either device, it syncs. In any case, I've overwritten the one on GD with the copy that opened locally, and now it's opening directly from GD again on the desktop. Very strange, but yes - I have a few copies now, just in case :)
Thanks Paul. Opening it from a copy stored on my HDD worked. I'll try deleting the one on GD and putting this copy in it's place. Strange that my Android device didn't have a problem with opening it from GD though.
This morning, rather unexpectedly, I could not open my KeePass file which is stored in Google Drive, using the Google Drive desktop app. Normally I just dbl-click on the file, and the KeePass password entry screen appears. Now I'm getting the attached error. Oddly, if I go to my Google Drive via my Android phone, and select the same file, it opens without problem in KeePassDroid. Thinking there might be some synching issue, I downloaded the file I'd just opened on my phone, copied it to my desktop...