Jumpy mouse pointer when system gets busy

[MisaMilosevic]

I have successfully installed iDeneb 10.5.5 on my PC (see configuration below) with Vanilla default kernel. No drivers outside the installation disc were installed except for ATI Radeon HD 10.5.x kext but it is of no importance as the problems appeared later. After a month or so of flawless fucntion, my mouse suddenly became jerky and jumpy when the system gets busier (i.e. scrolling pagies in InDesign, loading complex pages in Safari etc.). While moving the mouse, the pointer stops until the system finishes i.e. scrolling and then jumps to the position where mouse stopped. Again, it would appear only after the system had been working perfectly for weeks. And I also notice the sound becoming distorted.

Examining "About my Mac" says there's only one core! What could cause this annoying problem?

No updates nor third-party extensions have been installed.

 

Thank you in advance for your kind help.

 

Intel Core 2 Duo 2 GHz

Asus P5K

ATI Radeon 2600 HD

4GB DDR2