I've had a video that was uploaded on March 5 stuck on "under review" ever since. Tried re-submitting today with no effect yet. I tried submitting another, older upload and it too is taking much longer than usual under review (almost an hour so far). Usually I've found them approved within 30 minutes.
There seems to be a systemic problem with monetization over the last few days, based on other reports I'm reading on here.