Very slow when reading messages in inbox

I have a couple of email accounts set up and one of the accounts is horribly slow when I try to read the messages in the inbox. This is the only folder that is slow, and it happens with new or old messages. I have archived old messages, compacted the folders, etc. with no difference. I have also tried restarting Thunderbird in safe mode. I am running the latest version on Windows 7. Please help!