Strange Live-CD failure

[Richard Owlett]

I have:
    two machines - Lenovo ThinkPad T43 laptop and Lenovo 
ThinkCentre desktop
    two copies of the Ubuntu 10.10 Live-CD
In the past I had no problem with either CD running on 
either machine.
This morning neither would run correctly on either machine.
Everything fine until the large menu giving choice to run 
from CD or to do an install.
Clicking on run would trigger the little circle with moving 
dots indicating "busy". It would never get past that point - 
all combinations of CD and machine.

I'd just acquired a second laptop and tried both CD's. Both ran.
Now both CD's run on both of the original machines.

Obviously I've a physical problem of some sort.
Any (useful;) ideas?
TIA