Is it any particular key that causes the problem?
You might, for instance, have the backspace key defined as <del> (also known as ^?) which might, in turn, be seen by Linux as "interrupt". That would cause the sort of problem that you seem to possibly be describing.
First enter "stty -a" and look to see how "intr, quit, erase and kill" are defined.
If you can get to a shell prompt this is easy to test. Enter the command "cat -v" and then press whatever key might be causing problems. (Use ^d or whatever stty says "eof" is defined as for the key to exit "cat".)
If you don't know what I'm talking about you should find someone who knows about Unix & Linux to help you.