mcrypt hanged my 2.4.16

[Jacek =?ISO-8859-2?Q?Pop=B3awski?=]

I use kernel 2.4.16 with ext2 partitions. I wanted to crypt big (1.4GB) file
with mcrypt. It was long work, so I leaved my room. When I was back - system
was hanged with message like "invalid operation (...) process: mcrypt".
I don't know if it has something in common with kernel version, but why I could
hang system as a user? (mcrypt is not +s)
I will run mcrypt again, and if system hangs I will try to rewrite full
message.