engine or tranny?

1997 LEXUS ES 300.
I was on the highway driving last night when I noticed a little bit of a surge in the car it was not that noticeable but within a 1/4 mile it began to lose power like the tranny wasn't pulling i had decelerated from 65 to around 40 MPH, at this point the tranny was barely pulling so i pulled it from drive to 2nd gear and i felt it engage at this point i was heading for the side of the highway to get out of traffic as i pulled off the roadway it died, there was no noise at all that I heard that would indicate some catastrophic failure now the engine seems to be locked When you try to start it you can hear the starter engage, but it won't turn the motor. Today I took some tools and went and looked at it in the daylight, I put a wrench on front bolt of the crank and was able to turn the motor about a 1/4 turn one way then back again but that's as far as I can turn it. I also took the cover loose on the timing belt to see if it broke but it was intact and still nice and tight. I'm thinking something in the tranny is keeping the engine from turning but i,m not sure. Any ideas, anyone ever had this type of problem?

have you resolved this issue? what was the main problem? please let us know