There are three diagnostics Can't call method, to wit:

• Can't call method "%s" on an undefined value
• Can't call method "%s" on unblessed reference
• Can't call method "%s" without a package or object reference

Which did you get? The first is most common in my experience, and is usually caused by the object creation failing. But this is just a guess. You would get better help if you gave us more to work with than "I got this error message. Why?"