SOLVED! 
As Ulf had suggested via PM, I checked the MSVCR100 and MSVCP100 dlls in the /windows/system32 folder. They had somehow become corrupted. A quick re-install of the Visual C++ redistributable package (available on the Microsoft download site) solved the problem!
Just thought I’d post that here in case some of you run into this.
Thanks a lot Steinberg for latching on to my problem so soon! 
(And in case someone’s wondering - this solution post is so late not because of Steinberg’s response time, but simply because I was on holiday… 
)