Red triangle, check engine, hybrid warning -- what now?

Hey folks-- I've been utterly thrilled with my 2004 Prius that I've had for about a year. Never a moment's trouble, then today, right when I need it least for several reasons, I've got:

Red warning triangle
Orange engine with "Check"
The car shape with ! on MFD that I believe means hybrid system

This is clearly not good, particularly since I have to drive home (15 miles), and rely on my car every day. Is this something so severe that I should believe the manual and stop driving immediately? Should I drive home today?

Any advice on what this might be? I'm going outside now to see if the inverter coolant is rippling. This is all happening 5 days before I leave the country for a vacation, too. What fun!

 

Thanks! The helpfulness around here is only exceeded by the astonishing speed of replies! I just went out to check inverter coolant -- it appeared to be properly in motion. And now all three lights have gone out. I don't quite get that.

I will definitely check the fan and the oil, though I'm not sure what you mean by the cooling fan in back. I guess I'm still getting up to speed on all the weirdnesses of this car!

 

For what it's worth, this is the first 70 degree day we've had since, oh, last September or so. Don't know how that might affect inverter.

 

Okay, will do. Seems wild to me that one minute I'm having lights that call for heading directly to the mechanic, and the next there's nothing! I mean, I'll take it for sure, but does this tend to point to trouble whose arrival is merely delayed?