index of range, but data prints out

[mrc06405j]

I have written a program in python. It occasionally gives an index out of range at a particular line in the code. I printed out all of the variables referenced in the offending line and they all printed out fine. I am thoroughly confused. How can all the indexed variables print out in one line and then raise an error in the next.

Can you offer any help in debugging this problem?

Thanks,
Michael

PS - I am happy to give you the code and any other information that might be helpful