LME prediction - object not subsettable?

I fit a random effects linear model to data, and then tried to use it to predict, but I got this error:

predict(lmeObject, newdata, level=0)

Error in eval(mCall$fixed)[-2] : object is not subsettable

This is a new error for me.  It still occurs if I change the level to 1 or if I change the data for prediction back to the original dataset to which the lme model was fitted.

Can anyone help?

Thank you in advance!

Rebecca