So, I thought I would post a quick note for anyone that might one day have this problem.
Symptoms: My spiffy Performance Analysis spreadsheet suddenly decided it did not want to open. Yeah, 1 week to SfN and not good. Excel would open with a blank screen. I could click stuff and it was responsive, but the center was completely blank, regardless of whether it was opened with a document or just launched with a 'blank worksheet'. Nuttin there.
System specs: Vista (32-bit), Office 2007, all updates etc installed.
Resolution: I don't know what caused this, but launching Excel as Administrator clears it up. Just navigate to your Office folder (C:\Program Files\Microsoft Office\Office12\), right click on excel.exe, and choose "Runs as Administrator". Voila! Yer welcome. I don't know if it resolves it entirely (that one launch clears up all future launches), but it works well enough to allow you to use the program.