If it is taking such a long time to run the sim, it is most likely to be oscillating at high frequency, or calculating extreme conditions due to something you missed - I occasionally get Kv's and 100's of A, because I missed something. Try running the sim with a very short simulation time, you might be able to pick up the first few cycles that way if it is oscillating. If it's running for more than maybe 30s, it's usually a sign something is wrong, unless the circuit is complex (which yours isn't).
Also, simulators aren't perfect. Just occasionally (and it is very rare) you do get completely bonkers results. But again, the suggestion if you do is to figure out why - it more than likely due to poor design.
Go over everything extra carefully, I can see Q1 and Q2 forming a short circuit across the 25v supply if the input is not either fully high or low. U1 is going to have a serious problem unless it's one of LT's "C load" devices due to the 1uF capacitor across the output. Those are just the immediately obvious things. You should probably give your voltage sources some internal resistance, also.
I would try breaking the circuit down into sections and simulate each of those, before running the whole thing at once. Also, since it is a DC circuit, try decoupling all the amp inputs - if it is oscillating, this should reduce it enough to actually get some result you can see.
Other thought is, try a different simulator. LT Spice is generally the most accurate, but I have occasionally found Tina to be more useful (certainly easier to use).
Hope this helps