My GF drives a 94 1.8 SOHC 5 spd Pro, last night we heard a "pop" then what I swear to god sounded like a thrown rod...it ended up being a belt that jumped off the waterpump/alternator,wrapped itself around the PS pump and into the belt..
after 5 hours in a parking lot cleaning all the debris out and changing the belts (the crap was everywhere) its fixed and runs fine. The belts were changed not even 9k miles ago, non of the accessories are bad (ie no bad seized bearings) and all the pullies are straight and burr free...wtf?

 

If all of the pulleys are stright it could have just been a bad belt.

 

ok....it was just the oddest sound considering it was a belt...i heard it and thought:rod knock,collapsed lifter,brocken rocker or dropped valve.....