Hi alfonsolftc
nah - this error response is pretty clear about what the problem is. also - your ReadyAPI! version shouldnt have any impact - your java runtime may be an issue (version of JDK/JRE) but not ReadyAPI!
as I mention before - it's when it finds a class at compile time but on runtime the class is missing -either you're not using the correct import dec or the associated .jar file is non-existent, incorrectly named (unlikely) or it's in the wrong directory.
without sitting in front of your laptop - im almost 100% thats the problem
on a side note - is there a reason you're trying to use groovy to source your data from a spreadsheet rather than use the Data driven functionality available within ReadyAPI!?
if you cant use the data driven functionality - looking at your script - it just appears to find the spreadsheet, iterate through each cell and grab a single value? is that correct? it might be easier to source the value from a .txt file or .csv and then you don't have to bother trying to import all these additional classes for handling a spreadsheet?
the soapui help link might give you an easier way forward
nice one!
rich