Asus A7n266 jumper issues

Greetings all, its been a while since I've posted to this board. I ran into a problem setting up a board that came out of a perfectly working system. Here is the deal Asus a7n266 Socket A mobo, 512 Mb of ram, was running an athlon 1900, I tried a 2700 to no avail. Then after many jumper settings I put it all back to default and now it wont boot the 1900. I tried several other chips both athlon and duron, it sees almost anything under 1400 fine, boots it fine. (all blue chips) but the maroon ones, or green ones my pci mobo tester comes up as Failed board. I've got the install manual from asus, and the latest bios they have.