This same thing affected me too, it occurs if there is any mismatching of RAM.
Boot 9 and run DIMM first aid freeware if you want to see more information and get accurate feedback.
I was wondering how ASP could be wrong for so long, and if X didn't throttle back memory some how given the people that were having issues with some non-apple memory when the initial swith from 9 to X came....part of me (the litlle paranoid consipiracy theory beleiving part) thought maybe it throttled back performance to work across more systems...don't know if physically this is even possible, as I don't understand the mechanics of what is being measured or queried to generate the report...
But, since in 9 and with a 3rd party app I get to see PC-133, i'm cool with it for now and have left my tin-foil hat off for the day...