A number of users who have upgraded and jailbroken 1.1.4 are reporting that the Mail application stops working properly after the upgrade and/or jailbreak is complete. These reports of a broken Mail.app come in a variety of forms. For some users, Mail crashes when they attempt to open it. For others, it simply fails to download any new messages. Still, for others, Mail crashes when attempting to read a message.
FIX : Install SyncFix via Installer.app
1. Open Installer and add the iClarified source (http://installer.iClarified.com)
2. Install SyncFix (under dev 1.1.3)