We've upgraded to 7.5.4.2 too and it turns out that this old bug is still in there.

Allmost a year ago I did explain what causes this behaviour. It cannot be resolved by recalculating. It has to do with deleted users. At least that's one cause for this behaviour.

Try these steps yourself to reproduce the problem and you'll know where it comes from:
1. Create a new account
2. From this new account, send a PM to your own admin account
3. Log out the new account
4. Log in with your admin account (see the PM icon flashing)
5. Open the PM list and check if the new PM was received but do not open the new PM
6. Go to the admin section and delete the new created account
7. Go back to the forums

Now your PM icon should still be flashing, but you won't see that last PM listed anymore if you go check your PM list. The PM just magically disappeared

I've attached the updated delete.inc.php which I created to solve the problem once it arrises. But ofcourse it would be better to prevent this from happening at all. I just don't know the software well enough to handle that.

Thanks for posting. I did need to edit this since we can't have full scripts being posted. That being said, the 7.5.5 update might help on this problem as we found a few issues in how we were handling this.

We do have this fully tracked down and fixed for 8.0 as we restructured this whole bit completely.

Sorry about the full script. Won't happen again.

Have you (or anyone else) actually tested if this procedure as described above is now solved in 7.5.5?

i have, since i found what i thought was a bug in the way it used the mysql interface..

when i made the change, the problem no longer happened.. and it wasn't a hard/fast bug.. ie: reproducible 100%.. it was elusive and left to chance kinda dealio..

i assume that change (or something similar) is what is in 7.5.5

Linky Poo to what i ran across.. in reality, it all started with birthday emails (for me, at least )

There are actually a couple other issues with the flashing envelope as well, and I do know that it did resolve one of them, but not sure if it fully addresses what you've caught so your change might still be needed for now.