Can't input text, send in message window

Question

When creating an outgoing email in Mail (both new and replies), I can only type about 5 characters in the main message area before I get a "clonk" system error sound. At the same time, I cannot enter anything in the Subject field. The system is not frozen, as I can still input addresses. But when I click Send, I get the same system error sound.
I have two accounts set up on my iMac. Both accounts have .Mac email accounts using OS X Mail, but I only have this problem with one account on this computer (i.e., I can send email fine from the second account.)
Any help will be appreciated.
iMac (Flat Panel)   Mac OS X (10.4.8)   iMac (Bondi Blue Rev. A)

Answer 1

This problem in Mail is usually caused by some Launch Services cache or preferences corruption. The following article describes how to manually reset Launch Services -- the notes at the bottom of the article also provide information about the side effects of deleting each of the files involved:
Resetting Launch Services
If you prefer using a cache cleaning utility instead of following the manual procedure described in the previous article, this other article provides links to some utilities that can be used for troubleshooting and cache cleaning:
Resolving Disk, Permission, and Cache Corruption
It seems that the most appropriate utility for solving this particular problem is Tiger Cache Cleaner, but you may also want to consider other utilities, such as OnyX, or Cache Out X, which are free. Whatever utility you choose, be sure to read this first:
Side effects of System cache cleaning
As an example, this is how you should proceed with OnyX:
1. Quit all applications.
2. Launch OnyX and enter your administrator password.
3. Click Maintenance. In the Reset section, check LaunchServices database.
4. You may uncheck any other pre-checked options if you wish.
5. Click the Execute button.
6. Restart the computer.