[R] predict.lme / nlmmPQL: "non-conformable arguments"

[David Reitter]

I'm trying to use "predict" with a linear mixed-effects logistic  
regression model fitted with nlmmPQL from the MASS library.
Unfortunately, I'm getting an error "non-conformable arguments" in  
predict.lme, and I would like to understand why.

I have used the same call to "predict" with "glm" models without  
problems. I assume I'm doing something wrong, but I have no idea what  
it is. If someone could help me (even by telling me how to trace this  
properly - is there an interactive tracer/debugger I can use?),  
that'd be fantastic.

Here's what I'm doing:

 > summary(model)
...
Random effects:
Formula: ~log(distance) | target.utt
...
Fixed effects: primed ~ log(distance) * role * source - log 
(distance):source
...

 >  x=10:500*0.1
 >  new <- data.frame(distance=x, role="r", source="m"  )

 > yp = predict(model,  newdata=new, type="response",  level=0)
Error in X %*% fixef(object) : non-conformable arguments


 > traceback()
4: predict.lme(object, newdata, level = level, na.action = na.action)
3: predict(object, newdata, level = level, na.action = na.action)
2: predict.glmmPQL(model, newdata = new, type = "response", level = 0)
1: predict(model, newdata = new, type = "response", level = 0)