In the Mail app, it seems about half the time i start up (I have Mail set as a start-up app) it tells me that user "my name" already has the file open, and opening it can cause the file to become damaged. I have the choice of quitting or open anyway. I always just "open anyway" and there doesn't seem to be a problem with the file. Why does OS X think I already had the file open?
same thing happens to me, but only when i'd previously been booted into 9.1 on the other partition... i had assumed there was some connection there ... i then usually quit and log out and back in again ... i've let apple know about this, hopefully there'll be an update soon... :)
This Happens quite often to me as well. No tie-in with having been in 9.1 in my case, however.

I, too, just open anyway and have seen no ill effects - knock on silicon.

Apple has my feedback too. Let's hope an update fixes this as it is quite annoying (much like the trash priv thing)...

You know, when you go to empty the trash and it tells you that you don't have sufficient privileges to delete certain items. Even with admin power.
Hasn't been a big enough pain in my ass to try to troubleshoot or research this yet.
hmmm... so that's what you mean ...
i've only ever had that once so far... i just rebooted into 9.1 and trashed the stuff there ...:)
so... not really too big a problem for me either ...
Yeah. The reboot to 9.1 does work to trash the stubborn buggers...

Currently I am swamped but maybe next weekend I'll look into this - as Apple has not responded to my feedback/bug reports.

Maybe I could even write one of my first apps (My UNIX/Cocoa/etc library is growing) to fix this. Probably just me being naive though. We always overestimate our own abilities....