It basically is your processor's fault in that it is not the 333 that can take higher amounts of ram and run X.
Read this thread
http://www.macfixitforums.com/php/showflat.php?Cat=&Board=Forum19&Number=574835&page=0&view=collapsed&sb=5&o=31&fpart=
I ran into that problem with a Lombard I purchased used but was lucky to find a replacement from a dealer who didn't know the difference.
Here is some info from a thread which sorts out the various processors...
"Additionally, 3 affected, 3 "very likely to be affected" and 3 unaffected Lombards were reported in Japan.
ID / 333 or 400 / compatibility with OSX / CPU / serial / from TattleTech / purchase date
++++++++++++affected (3)++++++++++++
25/333/no/PowerPC 750L(LoneStar,Rev2.2) Copper G3 PVR=0x00088202 /QT931027EXW / + Date Manufactured = 99.8.6 + Location Manufactured = Taiwan/1999.8.7
27/400/no/PowerPC 750L(LoneStar,Rev2.2) Copper G3 PVR=0x00088202 /QT9252Y6EY8/ + Date Manufactured = 99.6.25 + Location Manufactured = Taiwan/1999.7.7
29/400/no/PowerPC 750L (LoneStar,Rev2.2) CopperG3 PVR=0x00088202 /QT925200EY8 / + Date Manufactured = 99.6.25 + Location Manufactured = Taiwan/1999.aug
++++++++++++ very likely to be affected (3) ++++++++++++++
24/400/installaion ok. But unusable due to many freezes/PowerPC 750L(LoneStar,Rev2.2) Copper G3 PVR=0x00088202 /QT9231SWEY8/ + Date Manufactured = 99.6.11 + Location Manufactured = Taiwan/1999.june
26/400/install ok. But freezes after a while./PowerPC 750L(LoneStar,Rev2.2) Copper G3 PVR=0x00088202 /QT93902ZEY8 / + Date Manufactured = 99.10.1 + Location Manufactured = Taiwan/1999.10.2
28/333/Not tested with X. Many freezes on 9.1 which cures by removing the upper 256MB/PowerPC 750L (LoneStar,Rev2.2) CopperG3 PVR=0x00088202 /QT936001FRJ /+ Date Manufactured = 99.9.10+ Location Manufactured = Taiwan/1999.9.14
+++++++++++unaffected (3)+++++++++++
23/400/ok/PowerPC 750L(LoneStar,Rev2.2) Copper G3 PVR=0x00088202 ///1999.7.19
30/400/ok/PowerPC 750L (LoneStar,Rev2.2) CopperG3 PVR=0x00088202 /QT92528EEY8/ + Date Manufactured = 99.6.25 + Location Manufactured = Taiwan/1999.aug
31/333/ok/PowerPC 750L (LoneStar,Rev3.1) Copper G3 with 10x PVR = 0x00088300 /QT9265NPEXW / + Date Manufactured = 99.7.2 + Location Manufactured = Taiwan/1904.1.1"
In short, Apple will not do anything to help you at this point. Your best bet is to try to find someone with an old Lombard processor that they may have taken out due to an upgrade. I doubt you want to invest much money in a new processor at this point.
Good luck.