Running 4.5.5 OSS on OS X PPC

I am having this problem with only one account, but logging into the web interface and IMAP are both hanging, but POP3 is working.

# telnet server 143
Trying 10.0.0.1...
Connected to server
Escape character is '^]'.
* OK IMAP4 Ready server 00022053
. login user@domain.com pass

[hanging for about 5 minutes now]

I did the identical thing with another account and it logged in just fine, while this particular account above is still hanging.

The web interface for that account hangs at "Loading..."

Tomcat seems to be eating up 98% of the CPU.

What could be going on? I don't see any errors in mailbox.log