This used to happen to me when I was using the popular 2x128MB HP memory with my 060/240Mhz BPPC. Switiching to a different brand solved the eventual freeze that I was experiencing with the HP memory. What worked for me is a pair of 50ns 64MB modules as well as a pair of (not HP, but PowerMem) 60ns 128MB simms.
It's possible that your ram is kind of intolerant whenever extensive usage of 603e occurs.
