that sounds like a very frustrating bug. :( i have tried to reproduce it on two machines but have thus far been unsuccessful. i'll do my best to find it!
This is not a bug per se, it's due to the
limitation of number of simultaneous keys
able to be pressed on certain rows of certain
keyboards. As mentioned above, the ability
to rebind should fix this issue as it will allow
people to play with different combinations
and find the keys that work with their
keyboard. I've also seen the issue fixed by
coding direct hardware key reading routine.