M-Audio Firewire 410 disappeared from VST connections

Cubase 5…My M-Audio Firewire 410 suddenly disappeared from the VST connections on all songs and projects after many hours of successful use. I tried reloading new drivers for the M-Audio and also reinstalled Cubase 5 but no luck!
What happened?? Stuck in the middle of a mixdown project!!

Switched on the interface after staring Cubase…? Don´t know - you screwed it
Mac…? PC…? Correct driver still selected…? any useful info at all…? “Reloading new drivers” means Downloading, or re-selecting…?

thank you for your info. Some how the VST device setup switched itself from M-Audio firewire to internal audio.
Live and learn! back to work.