locking in oracle

hi guys ,

i am working with oracle8i .the probelm with me occasinally system is automatically locking the tables i guess .i experienced this two times and when i went to v$lock and saw which command was locking the table i felt surprised to see a simple select statment had locked the table .could you guys please help me out in this i had to kill the session using orakill to get rid of the lock .pls share if any of you had similar experience .

thanks
rajeev