I recently sicken of Windows 8 Metro. It sucks. However, I had Ubuntu 10.10 dual boot and works super stable and fast.

Just yesterday a window popped up notifying about 12.04 update. I go all the way for it. I was new to Unity shell and everything, but google is great and I soon get accustomed to it. Heck, I like Unity.

However, when I started Software Centre, suddenly the whole system lagged painfully, I barely moved the mouse. I waited a moment, when I hover the cursor over the app list, it seems distorted. So does the desktop, the Dash... everything.

Any workaround for this issue?

Here's the specs, pretty ancient:
Video card: Intel® 945G x86/MMX/SSE2
CPU: Intel® Pentium(R) 4 CPU 3.00GHz x2
Ram: 1.5 GHZ