1GB RAM and Mouse don't like each other

Been having this strange problem since upgrading my main system to 1GB RAM from 512MB. Both of my systems are on a KVM swtich and my main system has had the upgrade. On first boot up the mouse wouldn't respond, checked the cables, all was fine. Re-started, same again. So use the Keyboard to re-install the Intellimouse drivers, re-booted and was fine.

Then booted up again and the mouse wouldn't move, so did the same thing with the drivers again but it didn't fix the problem.

So I hooked up the mouse and keyboard straight to the system and not through the KVM, booted and mouse was fine and WinXP Pro said it had detected new hardware (the mouse), so did another re-boot and it was fine. Thought I'd fixed the problem so hooked up the mouse to the KVM again and guess what, doesn't work.

Sorry about all the re-booting:D This worked fine with 512MB ram but it doesn't like a GB. Any ideas?