Umm...Apple CLEARLY states that OS X PB needs 128MB. When you order it (its on the order page), on it's website for OS X PB, PDF literature, in the Box OS X PB came in.
Either
1) Your G3 is in some unsupported configuration (Firmware update?) or...
2) You pirated your CD and asked the question in such a manner as to hide that fact (if this is the case it NEVER worked)
Solutions:
1) Update your Firmware
2) Go buy a legimate copy of OS X beta