How to unflag messages on Mail?

I have just bought a new MacbookPro with Lion and I do not seem to be able to unflag a previously unflagged message on Mail. The flag would disappear but magically reappear after a few seconds. How can I get rid of teh flag without deleting the message? Thanks!

I am the OP. It seems that the problem exists with the messages that I imported from my old Mac... it is as if they had become inherently flagged...

I noticed you can unflag by clicking on the flag the message currently has or selecting the cross to the right. Have you tried both ways of unflagging? What you could try too is to select a different flag - so even though it's flagged already, flag it again and then try to unflag with one of the ways above in my first sentence.

Does that help at all?

Nope. I have tried them all but the flag keeps coming back. It is quite annoying!