Can't compose, reply or send mail - but can receive

Question

My software is up to date and I can receive mail, but I select reply and it usually would bring up a new mail window and won't or I try to compose a new email and my mail won't let me even type past the third letter or send/forward/reply to anything.
Worked yesterday fine - the only thing I did was delete some fonts, but replaced them and restarted and mail still won't work - but I can receive and all of my other programs are uneffected.

Answer 1

This problem in Mail is usually caused by some Launch Services cache or preferences corruption that affects the built-in spell checker. 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, take a look at this other article for general troubleshooting and cache-cleaning procedures. Actually, you should also verify/repair the startup disk (not just permissions), as described there:
Resolving Disk, Permission, and Cache Corruption
The most appropriate utility for this particular problem probably 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. Go to Maintenance > Reset and check LaunchServices database.
4. Un-check any other pre-checked options.
5. Click the Execute button.
6. Restart the computer.