A virus? That number look suspiciously like a date...

Hmm... '19990305' error leads to No Bootable Device on some computers including IBM (which Ambra is) . Have you gone into the BIOS to see if it still shows a floppy drive and does it match the type (assuming 1.44MB)...
Does the BIOS have the correct Date/Time ?

The BIOS does keep the correct Date/Time, but has always thrown error messages at boot (CMOS values corrupt, and configuration error). I can go in and manually select the correct A drive (3.5", 1.44mb) and it shows under system summary, however upon the next boot it is disabled. After leaving it alone for a couple hours it actually booted to DOS twice (once from startup disk and once from the hard drive), but all subsequent attempts resulted in the '19990305' error. Could this just be a totally dead Dallas clock chip? I didn't think a dead CMOS battery would prevent it from booting (sorry if this is obvious, this is new to me).

My Ambra (a Sprinta 1) also has a dead CMOS battery (scrub that, it has no CMOS battery after I yanked it when it started leaking) but boots just fine after I update the BIOS settings when its powered up. Actually, might be a good idea to check yours to make sure that battery isn't in the process of leaking all over the board (assuming its a Varta type and is still in place).

Yes most DALLAS can keep time but not hold CMOS settings when the battery gets low (just before failing), it is one indicator of the internal battery being below 3v.
The clock can usually run down to about 2.7v but the CMOS cannot keep refreshed at that below about 2.9v from my experience. Yes either mod the DALLAS with external battery or buy a new one.
Which Dallas RTC is it ?

Thanks for the help! its a Dallas DS12887, I think I will try the external battery mod first

After doing the external battery mod, the 'CMOS values corrupt' error is cleared. However the 'configuration error' persists, and system configuration isn't stored. From what I understand the CMOS ram is actually stored on this IC. I ordered a new Maxim DS12887+ replacement so that will hopefully solve the problem.

Have you tried clearing the CMOS settings using whatever jumper is the official clear jumper? It's wasn't the same machine, but I think there was a recent thread where someone was still having problems after replacing a battery, which were fixed once they did a proper clear CMOS.
Re: IBM PS/1 2155-593 POST Error 164

I just wanted to update this post if anyone runs into this in the future. Replacing the Dallas real time clock fixed the CMOS ram issue as well as the failure to boot.

Thanks again for the help!