please post back w/ more detail on the differences between the two computers, like what operating systems they are using, and also please post the code that you are referring to. can you pinpoint any certain part of the code that is causing the problem on this other computer?
when you run the macro on the win98 machine, and you get the error msg, does it give you the option to debug the code? if so, when you click 'debug', is there any particular line of this code that is highlighted as the place where the code started to error out?
could you please post the extra_profes code as well - this may have something to do with your problem. since the only thing that you worksheet_change event codes does is call this other macro if you are in a certain target.cell, perhaps we need to be looking at that macro as well
then try using a different event to trigger the macro, like Worksheet_Calculate(), and see if you still have the same problem on your win98 machine. not sure why the worksheet_change event would not work on your machine