My friend's 50001R seems to reject original GS2 PS2 and PSX discs, the Iomega/Interact Memory Manager Plus, and USB Sharkdrive Zip drive. In fact it locks up whenever the [fully functional] Zip drive is plugged in. It RSODs on the GS2 and MMP and we even tried booting via codebreaker and it still said invalid disc. Am i not aware of something here or is it just his PS2?
PS: the system is unmodded, no swap tricks or anything.