Windows 7 Enterprise x64 + Opera 11.x + youtube results in complete system freeze

Hello,

I've been a happy Opera user for more than 8 years now, but since v11 I'm experiencing the following problem:

I currently use this system:
- a Dell Latitude E5520 system (although this issue manifested before on a Latitude D830 exactly the same way, the D830 having nVidia NVS 140 graphics) with Intel HD3000 graphics drivered from Intel on 10.june.2011;
- 8 GM RAM (previously 4GB, but the issue is the same);
- OS Windows 7 Enterprise 64 bit, with SP1 (problem manifested also on the same OS type, without the OS service pack) - system installed from a clean setup disk, with SP1 included, not a service pack upgrade from the previous version.
- Opera Version:

User Agent:Opera/9.80 (Windows NT 6.1; U; en) Presto/2.10.229 Version/11.60
Build number:1185
Popups:Block unwanted
Java:On
Plug-ins:On
JavaScript:On
Referrer logging:On
Proxy:Off
Encoding setting:
Display mode:Strict
Load images:All
Normal cookies:Accept
Third party cookies:

- the current Opera instance has been upgraded from v9.<something> to date in steps, each time a new update was available. The reason is that I wanted to keep all the browser configs and wand passwords.
- I always let the system propose & install the available updates for the Flash player and Java runtime, so these are up to date.

Since installing & using Opera v11, the system crashes completely when I view youtube videos in full screen.
In fact, the system freezes, with the last bit of sound (a few milliseconds of it or so) looping out the sound card.
The only way to recover the system is by a hardware reset.

The biggest problem is that I am not able to find any useful information in any logs.
I browsed the Windows event viewer, with no success (the only related info was that "The previous system shutdown at 10:59:40 AM on ‎12/‎8/‎2011 was unexpected.", which was caused by the reset action).
I can't find any Opera log to look into.

Has anyone met this kind of problem before?
Has anyone found any useful information / workaround / solution to this?

L.E.: The crash happens randomly, after allowing me to watch somewhere between 5 and 60 minutes of youtube video in full screen.
Also, I regularly use several common programs at the same time, like Thunderbird, some messenger clients, IE and, maybe most notable, a second instance of Opera, updated to the same version, installed on a different path and used for a completely different set of web pages.

Thanks,

--
Alin F.