I don't recall you saying which OS you are running but I'm guessing that it is down in the OS 9.x.x range.
There is a possibility that the HD is becoming full. Do you know how much space you have available on that drive? How much RAM do you have installed? What Revision G3 (blue and white) is it?
I know, lots of questions but the answers may help. If you are running OS 9, go to the Apple menu and run Apple System Profiler. That will tell you how much RAM you have installed, how big the drives are and how much space is available on it. Drive sizes are under Devices and Volumes. You can get the same information in OS X by running the System Profiler too. To find the Revison/version of your machine, open the side case and look inside. if the ribbon cable connecting the Hard Drive to the Logic Board (Motherboard) only has the one connector(Not counting the one that is plugged into the logic board), then you have Revision 1. If it has two connectors, you have Revision 2.
The reason for this question is that the Rev 1 machines did not really like having another Hard drive installed into them but the Rev 2 ones had no problem with it. Just in case you need to install a larger HD.
Depending on the amount of RAM that is installed, and if you are running OS 9.x.x, you might want to look at the amount of Virtual Memory you have set. In OS 9, go to Control Panels/Memory and punch the Use Defaults button. Optimum VM is 1 MB above the physical RAM.
Stop using Norton System Works! It does not know when it cannot fix a problem and goes ahead and "fixes" it anyway. Do NOT use it again.(pretty please)
Anyway, enough questions for the moment, pass on the answers and we can go from there