boy spectre really does ****, is it the only simulator you have available? how about hspice? or even better eldo?
in any case you are still not mentioning your accuracy settings, I guess you are using defaults, which would be bad since default accuracy is 0.1% in spectre
as of the latch, sorry I misread your diagram I thought latch indicated a latched comparator, how are you modeling the comparators?
The errors you are getting are from lack of convergence during tran, the nets implicated might be a good indication of where the problem lies
I am reading the presentation you are using as a reference, I will see if that gives me a better guess of where your problem might be