Omaha :
Could be lots of reasons - without more info it's difficult to know - post details of the computer you are having the problem with, i.e. Operating System, your Processor, memory, Graphics Card, etc. and which "bowser" you are using - all compared with the "good" machine.
As a start you could check that you have the latest drivers for your Graphics card and update them from the manufacturers web site - this can often cause the problem you are experiencing.
Coconutty