Comment 25 for bug 552246

There is another thread where several people are having the same problem, it seems the following video cards are also affected:-

Mobility Radeon HD 3650
ATI X1400
ATI HD4850
Dell Inspiron 1501 running radeon with an ATI Xpress 200M (just in case someone searches for their laptop name)

My experience is with an
Acer Aspire 3050 with ATI RS482 [Radeon Xpress 200M] so similar card as Original Poster.

Initially incorrectly labelled as radeonhd but corrected in thread to radeon driver.
http://www.backports.ubuntuforums.org/showthread.php?p=9313880

an additional work around in the above linked thread include:-

switching to another virtual desktop via Ctrl - Alt - right cursor key, then back if need be with left cursor key.

worked for me with default lucid install and desktop wall as standard, though I do have extra ticked in desktop effects and have disabled resume password lock via gconf-editor.