Errors with picklist after 3.0 switch

Errors with picklist after 3.0 switch

I'm not sure if this is documented somewhere and I've missed it but on loading a form with a dynamic picklist I consistently get an error message after the switch to 3.0. I get an error while executing "on user input" script, "unable to evaluate if/while condition", and a couple of variables are listed as null. This script worked without a hitch under 2.0. I tried putting in conditional statements to avoid the null, but it didn't seem to help