iMac DVD player

My new iMac won't play DVDs!
It's just a few months old and happily played all
my DVDs up until last night, and from various regions.
I got a warning that I could change region one more time before it would be locked, and the iMac asked what region I would like. I selected Region 2, but now as soon as I put in a Region 2 DVD I get a message 'You can change the region one more time...' and then immediately quits.
I have reinstalled Snow Leopard, and in Utilities started the Disk permissions repair thing but the problem is still there.
When I put in a Region 1 DVD it plays normally, as if
it's been set to that region, but why warn me I have one region change left if that is not in fact the case?
Any help appreciated!
It's just a few months old and happily played all
my DVDs up until last night, and from various regions.
I got a warning that I could change region one more time before it would be locked, and the iMac asked what region I would like. I selected Region 2, but now as soon as I put in a Region 2 DVD I get a message 'You can change the region one more time...' and then immediately quits.
I have reinstalled Snow Leopard, and in Utilities started the Disk permissions repair thing but the problem is still there.
When I put in a Region 1 DVD it plays normally, as if
it's been set to that region, but why warn me I have one region change left if that is not in fact the case?
Any help appreciated!