0x7B error installing Windows to Thinkcentre

I'm at my whit's end trying to get Windows installed via RIS to an IBM
ThinkCentre A55 (8705). The textmode setup seems to run fine, but
when the system tries to reboot into GUI mode setup, it blue screens
with a 0x7B error, which appears to be related to MassStorageDrivers.
I've added what appear to be the appropriate lines to my remboot.sif,
textsetup.oem, and winnt.sif files. But I'm still getting this error.

I've added drivers to my RIS image plenty of times (every time Dell
kills a perfectly good model, in fact) and had no trouble adding the
MassStorageDrivers for the SATA drives in the E520's I bought last
time.

I'm looking for any guidance, what so ever.