Serial monitor freeze with Mega on Windows 7

Hi everybody, Up until now I have been able to resolve my problems by reading this forum but not this time so here comes my first post.

My problem is best illustrated by uploading a simple sketch like Blink to the board and then opening the serial monitor. If I do this with my new Mega 2560 (R2) the led on D13 goes from blinking (caused by Blink) to solid for about 10 seconds and it then continues to blink. The Tx and Rx leds are off during the freeze. The behaviour is the same for any sketch I try this with. After the 10 seconds freeze, communication through the serial monitor works as expected again. The IDE version is 0022.

I have reinstalled the IDE ... no change. I have tried the same thing with a UNO board ... No freeze! I have tried the MEGA and the UNO from my Mac ... No freeze!

I need some help with this one. Any ideas?

yes, sounds like a driver issue to me. option: delete the mega serial driver and install it again.

I have deleted and reinstalled the driver/.inf but no joy. There is still a 10 s freeze with the D13 led on after opening the Serial Monitor. And as before, this only happens with the Mega 2560 (r2) (tried two boards) on W7. Not with the UNO on W7. Not with any of the boards on Mac. Very confusing and annoying.