Target Display Mode stopped working with my MBP

[csnplt]

I have a November 2009 27'' i5 iMac and a 2010 Macbook Pro 15'' i7. After installing the iMac's Target Display Update 1.0 and 10.6.4, I'm no longer able to connect the MBP to my iMac. When I plug in my mini displayport cable, the iMac's screen goes black for a few seconds, then the MBP's screen flashes blue for a second or two, and then back to normal, and finally, the iMac's screen goes blue for 5 seconds or so, and then back to the desktop.

What, if anything, can I do to fix this? Anyone have similar problems? I just tried reinstalling Mac OS X, but that didn't work.

Thanks for any advice.

 

[PlaidHatter]

Did you find a solution to this? I lost my ability to switch last night too! Resetting the SMC isn't fixing the problem.

 

[csnplt]

Did you find a solution to this? I lost my ability to switch last night too! Resetting the SMC isn't fixing the problem.

I actually just had to reset the PRAM on my Macbook Pro. It turns out the problem wasn't even related to my iMac. Hope this works for you, too.