[R-sig-ME] Error in lme.lmList (package nlme)

[Dan Bebber]

I am receiving an unusual error message from lme.lmList in the nlme package.
The dataset is not huge (1265 observations of 31 groups), and I can send it to others to check if required.

The lmList call appears to work OK
fm1 <- lmList(equdist ~ year |pest,  data)

however, when I try
fm2 <- lme(fm1)
I get
Error in names(madRan) <- rNames : attempt to set an attribute on NULL

This is a new error (I ran the models successfully a few weeks ago).
When I try
example(lme.lmList)
the error does not appear, so seems to be something to do with my data.

Any clues gratefully received.
Thanks
Dan