Resolved A Sony Vaio Laptop fails to display streaming video in full screen

It shows HULU, Youtube, and WIMP dot com videos in their boxed form just fine. When I click to go to full screen, I get, variously, either a blank black, or dark grey screen, or, more often, a screen divided into two triangles, with a straight line running from the lower left to the upper right corner. The resulting triangles are usually light grey(upper left corner) and the lower right corner is dark grey. On youtube, the triangles can be colorful(solid colors), depending on what the colors were in the original scene. Mostly, however, they are two shades of grey. Audio continues unchanged. Clicking the mouse anywhere on the screen pauses the stream. Clicking the escape key restores the boxed display, and I can continue with the video by clicking the screen that now has the "play" symbol displayed.
This laptop, a Sony VAIO has pretty good specs: an Intel Centrino Dual core at 2.53ghz per core. The video card is an ATI Mobility 3460 with 256megs of ram. System ram is 4gigs, even though the OS is Vista Home premium 32bit-so only 3 gigs(2.75?) are put to use. The display is set to native resolution of 1600x900-a 16.4" screen.
I have updated the BIOS and the video card driver to the latest. I am at a loss as to what to do next, other than try Sony tech support. This laptop is freshly restored via the recovery partition.
Thanks.

 

What kind of media player are you using?

 

Thanks Evan. Updating to Adobe Flash Player 10 did the trick. I am using IE 8.
As to Jilly's question about which player I'm using, I confess that I don't know how to tell. This laptop has Windows Media Player 11, Quick Time, several Sony Vaio media suites and programs, and some others.
I don't know how to tell which player "grabs" or pre-empts the others to display the stream.
Thanks again for your replies and help.

 

Outstanding. Might you now, please go to the lower of the two site toolbars and choose "Thread Tools: and in the drop down menu, hit the choice at the bottom: "Marked solved'?

Enjoy!