Hello Anup, I wasn't saying anything was wrong with hardware - I sure couldn't manage to replace my mouse each time it begins getting touchy. What I did say is that I've only encountered that error message when I've accidentally double-clicked the submit ... and I verified the problem was at my end by using the Browse features and checking to see If the new cat/subcat was added (yes, it is) and using Edit in Browse to check that the fields are correct (yes, they are). Even without saving again (selecting another cat/subcat in Browse), the cat/subcat is there working and configured properly.
How did the new record become available to phpadmin for saving "again"? I believe you're describing the very same phenomenon I've described - an inadvertant double-click on the submit. The first writes in the record, the second produces a timestamp error because the form and (now existing) record time no longer match.
I didn't realize posting my observations would cause so much anxiety. Apologies.