I upgraded my jailbroken 3.0 iPhone 3G to 3.1.2 last week and used PkgBackup to reload all my Cydia apps. Afterwards, I was having issues with the mail app. Not only was it draining my battery but it refused to update the mail inside the app itself. I have 45 emails in my Inbox on the email server, which all downloaded to my iPhone. I deleted about 1/2 of them and read the remaining emails on the phone. However, every time I relaunch the app, turn off the phone, or resping, it resets to the original 45 unread emails. I thought it might have been an issue from the PkgBackup, so I wiped everything out and did a jailbreak from scratch over the weekend. Unfortunately, I'm having the same exact issue. Has this happened to anyone else and is there a fix for it???