Computer slowdown web use

[gr00]

HI all,
i bought new computer 3 months ago. Configuration is:
Intel Core i7 860
H50
Gigabyte P55-UD3
DDR3 2000 MHz Mushkin blackline "daredevil"
Radeon 5850
Seasonic 750W S12D
Windows7 64
etc...
I've had numerous problems with it since I bought it, it was freezing regulary. But that is not a problem now since I've resolved it - another thing bothers me. When I'm browsing the web with a lot of open tabs I've noticed slight lag when trying to scroll the web page: eg in long pages when scrolling it lags for a half second and then scrolls, sometimes it lags again on the same page. When watching Youtube videos it happens that videos sometimes jitter: video hangs for half second while audio is OK (the clip is loaded full), regardless of open tabs. Happens in opera and IE (haven't tried other browsers, probably them too).
It happened from day 1. What I think is wrong is the RAM (again, it would seem). PC is tested with memtest and Vantage till I got blue (but computer didn't).
Is this normal by any logic? Any suggestions? If any one is interested I could post my freqs from BIOS, now ram is working on 150*12=1800MHz, and CPU is on 3.3-3.9 (turbo boost obviously).

 

[mpilchfamily]

How fast is your internet connection?

 

[Gunbuster]

video driver would be my guess.

 

[gr00]

Internet connection is not a problem (5Mbit/s), video is already loaded on that part, or fully loaded. Pages, either fully loaded or not - it happens. But even in not fully loaded pages it shouldn't be scrolling so unsmoothly (even the 5 year old pc easily behaves better in scrolling web).
Could be somethig with video drivers. I've had 8800GT in the same configuration and the PC was freezing regulary every day. It wold freeze never in a game , always in windows and most likely in web pages (it scrolled the same then). It was a nightmare for a brand new PC, after much complications I dumped my old 8800GT and bought a new 5850. The result is PC doesn't freeze anymore but the scrolling is the same.
As for the drivers it used to be latest NVIDIA. When switched cards, everything I knew about I cleanly uninstalled, even used some driver cleaner/remover. Now it's latest Catalyst. (Downloading THE latest now but I doubt it).
Could it be something with windows 7?

 

[HalfCrazy]

When I used the ati 10.5 and 10.6 drivers for my 5870 crossfire setup. I ran into problems where games would random freeze up or crash. Today I installed the new 10.7 drivers and had no issues as of yet. But it does sound like a driver issue to me.

If you happen to use firefox as your browser. They got a plugin where it will smooth the scrolling out some more.

 

[gr00]

Thanks for the replies. Will try new drivers.