Fatal Exception 06 means Invalid Opcode Fault.
Are you using a large build? Some NICs map only 8 or 16 KB of the ROM into the address space even though the ROM is actually larger than that (they need additional programming to swap in the remaining ROM pages). So if the offset address (the X:s in D800:XXXXXXXX) is higher than 1FFFh or 3FFFh, that would be a likely cause. On the other hand, if that is the case, I'm surprised that you would be able to go as far as installing and booting Windows 95 before the problem manifests itself.
Can you provide the brand and model of the NIC and also the build options you used (assuming you made a custom build)? I am also assuming that you have verified that the ROM was programmed properly.
Are you using a large build? Some NICs map only 8 or 16 KB of the ROM into the address space even though the ROM is actually larger than that (they need additional programming to swap in the remaining ROM pages). So if the offset address (the X:s in D800:XXXXXXXX) is higher than 1FFFh or 3FFFh, that would be a likely cause. On the other hand, if that is the case, I'm surprised that you would be able to go as far as installing and booting Windows 95 before the problem manifests itself.
Can you provide the brand and model of the NIC and also the build options you used (assuming you made a custom build)? I am also assuming that you have verified that the ROM was programmed properly.