Mail crashes whenever I try to reply or create new mail

Question

For the past 24 hours, whenever I try to reply to an e-mail, or create a new one, mail suddenly crashed. It is very reliable in this way; there are no exceptions. The the newest update/change to my configuration was the update of the 10.4.4 system stuff from Apple, followed a few days later by an update for the 15 in G4 Powerbook battery management.
Also, though not related to mail, the Software Update function does not work - "Can't connect to Update Server", and Safari will not load any pages - "CAn't connect to server...". However, Network Diagnostics says that I am connected to the internet, as does Firefox - it loads pages just fine! All other computers in our home network, including my G5 Tower, are performing and access the internet just fine.

Answer 1

OK. Verify/repair the startup disk (not just permissions), as described here:
The Repair functions of Disk Utility: what's it all about?
Do you have any Mail plug-ins or system utilities that could interfere with Mail? In the Finder, go to each of the following folders (if they exist). What do you see there?
/Library/StartupItems/
/Library/InputManagers/
~/Library/InputManagers/
/Library/Mail/Bundles/
~/Library/Mail/Bundles/
Note: For those not familiarized with the ~/ notation, it refers to the user’s home folder. You can easily locate any of the folders referred to in this post by copying the folder path here, doing Go > Go to Folder in the Finder, and pasting the folder path there.