Internet News Internet Investing Internet Technology Windows Internet Tech. I would suspect that some library or the ls file is corrupt. Try to copy them to a scratch area for readability test.
Memory fault is another possibility.
It could also have to do with grown defects on a swap partition. I'm not sure if your system supports superuser mode to have a look into this. I have another sco unix machine, same version and everything. I have tried different shells and diffrent accounts, all showing same error. It was just a guess.