Unfortunately I don't know of a good third-party memory test to recommend for a B&W. (Apple's knowledge base article about G3 RAM errors "helpfully" recommends "MacTest Pro", which was apparently only available to authorized service providers.) I had to determine that RAM was the problem empirically, which *sucked*.
(The problem appeared after I'd swapped not only the RAM but the video card, so it was a matter of pulling and replacing parts to figure out what the issue was. Eventually, and I forget exactly what it was, I found something that would "reliably" make the machine produce errors or panic if there was RAM it didn't like present. It might of been transferring a *very large* file via scp and running an md5sum on it. It'd either crash doing one of those tasks or the md5sum of the resulting file would be wrong. Of course your mileage may vary... and also note I managed to let the problem trash an OS X install before I gave up mucking with it.)
(The problem appeared after I'd swapped not only the RAM but the video card, so it was a matter of pulling and replacing parts to figure out what the issue was. Eventually, and I forget exactly what it was, I found something that would "reliably" make the machine produce errors or panic if there was RAM it didn't like present. It might of been transferring a *very large* file via scp and running an md5sum on it. It'd either crash doing one of those tasks or the md5sum of the resulting file would be wrong. Of course your mileage may vary... and also note I managed to let the problem trash an OS X install before I gave up mucking with it.)