For some reason the rules in Mail aren't being applied to incoming messages. I can right click on the message and hit Apply Rules, and everything is fine, but it doesn't do it automatically.
I have the same problem with applying rules to messages.
I filter messages to certain Sub-Folders on the IMAP-Server via sieve.
In the Mail.app Client I am coloring messages depending on the Subject.
This worked fine in the Tiger Mail.app.
Now with Leopard I have to either select all the Mails and "Apply Rules" or just click the message - then the colors are applied to the messages...