Anyone familiar with Mitsubishi 3.0l timing belt replacement trouble?

I have a '94 Spirit with 91K on the engine and found out the timing belt should be replaced at 90K when I was replacing a bad serpentine belt.  Once I got down to the timing belt, I figured it would be a good idea to replace the water pump after all that work since it's driven by this belt.  I installed the pump and got the timing marks lined up for the crank and two cam sprockets.  I put the belt on counterclockwise making sure the only slack was on the tensioner side and released the tensioner.  I then proceeded to turn the crank two turns to see if the marks still lined up but once I started, I could only turn the crank about 90 degrees before it stopped (I got the same result with the sparks plugs out and also with the timing belt off with both cams still on their marks).  The crank mark is at about the 1 o'clock position and I could only turn the crank to 5 o'clock.  I did have some problems getting the belt on because the cam for 1,3,5 cyls. (firewall bank) popped and slapped over several times to either side from coming off a lobe and had to reposition it many times.  I stuck a wire in the #1 cyl. to make sure it was at TDC, too.  Is it possible a valve head could have broken off or a valve guide fallen from this "popping" action of the cam? The car was running just fine before I tried this "preventative" maintenance.  I sure would appreciate some helpful input from anyone out there since I had to work on this problem most of the week of Christmas since the wife is getting frustrated from me driving her truck to work.  Thanks.