performance - Some apps very slow to load on Windows 7, copy & paste very slow

I searched here and couldn't find a similar issue to mine but apologies if I missed it. I've searched the web and no one else seems to be having the same issue either.

I'm running Windows 7 Ultimate 64bit on a pretty high spec. machine (well, apart from the graphics):

Asus M4A79T Deluxe

AMD Phenom II 965 black edition (quad core, 3.4GHz)

8GB Crucial Ballistix DDR 1333MHz RAM

80GB Intex X25 SSD for OS

500GB mechanical drive for data.

ATi Radeon HD 4600 series PCI-e

Be Quiet! 850W PSU

I think those are all the relevant stats, if you need anything else let me know.

I've updated chipset, graphics and various other drivers all to no avail, the problem remains. I have also unplugged and replugged every connection internally and cleaned the RAM edge connectors.

The problems:

Video LAN (VLC) and CDBurnerXP both take ages to load, I'm talking 30 seconds and 1 minute respectively which is really not right.

Copy and paste from Open Office spread sheet into Fire Fox, for example, is really, really slow, I'll have pressed control V 5 or 6 times before it actually happens, if I copy and then wait 5 to 10 seconds or so it'll paste first time so it's definitely some sort of time lag.

Command and Conquer - Generals: Zero Hour. When playing it'll run perfectly for about 10 or 20 seconds then it'll just pause for 3 or 4 then run for another 10 or 20 seconds and pause again and so on. I had the Task Manager open on my 2nd monitor whilst playing once and I noticed it was using about 25% of the CPU, pretty stable but when the pause came another task didn't shoot up to 100% like others on the web have been reporting (similar but not the same as my issue, often svchost.exe for them) but dropped to 2 or 3% usage then back up to 25% when it started playing properly again. Very odd!

But it gets even odder... I had a BSOD and reboot last week, when it rebooted the problem had completely gone, I could play C&C to my heart's content and both the other apps loaded instantly, copy and paste worked instantly too. I did an AVG update earlier this week which required a reboot, rebooted and the problem's back. I don't think it's AVG related though, I think it was just coincidence that's the app that required a reboot. I think any reboot would have brought the issue back. A number of reboots later and it hasn't gone away again.

If any one could make any suggestions as to the likely cause and solution to these issues I'd be most grateful, it's driving me nuts!

Thanks, Mike....