Our [hacked] iPhones rarely crash anymore.
However, these steps should help if/when there's trouble...
Try to keep at least 250MB of free space on your device for use as cache.
Reset the device using 'Respring'. (Or, run SMBPrefs, and tap 'Restart SpringBoard'.)
Turn the device off, and back on.
Create a copy of your devices backup file:
Apple Macintosh: Username/Library/Application Support/MobileSync/Backup
windows xp: (Note: the 'Application Support' folder is invisible by default.)
C:\Documents and Settings\Username\Application Data\Apple Computer\SyncServices\Local
(unsure of actual filename, backup the folder, just to be safe.)
For Safari, clear the history, cookies, and cache. (run 'Settings', tap 'Safari', scroll to bottom.)
Restore the device through iTunes. (You backed up, Right?)
Erase all content and settings: Run 'Settings', tap 'General', tap 'Erase All Content And Settings'. (You backed up, Right?)
Warning: This will erase all content and settings. If the problem remains, its not your content and/or settings causing the issue.