Ok - I mis-read the issue. In order to clean this up we need a smaller value for mod_time. The value that is in your corrupted prefs is much larger than the what the value should be for a pref update right now

115499352020
vs
1217943541

This means that we will need to do something to fix this issue since in order to correct this problem we would need to stop BOINC on every one of your computers at the same time while you go through and modify each computer while we also modify the database value. This would be tricky to co-ordinate (since I think you have a number of computers active.

I will consult with the BOINC developers and see what they think. We may just modify the logic so that if the mod_time is too far out in the future, then it is treated as invalid. But I want to make sure I'm not overlooking any negative side effects.