I just called OTCMarkets about SVEN. The guy I spoke with told me that it was a "systems issue". The stock isn't halted, and can in fact be traded, but the MMs aren't allowed to trade it electronically.
He wouldn't tell me any more than that, though I'm sure it's not the whole story. He said he expected things to be working normally by tomorrow morning.
No other stocks have been affected by whatever it is.