Can't Send/Receive with Thunderbird (Temp Directory Problem)

[NickD]

I haven't been able to receive or send any mail with Thunderbird. When I try to receive messages, it always says that there are none available, but people have sent them to me even days ago, and they won't show up.

When I try to send, I get an error message that says:

Send Message Error

Sending of message failed

Unable to open the temporary file. Check your "Temporary Directory" setting.

What is the problem here?

 

[Cromulent]

Tried repairing permissions?

 

[NickD]

Well, that fixed the receiving problem, but I still can't send. I get the same error message.