[AUCTeX] TeX-active-master not defined

[Mandar Mitra]

Hi,

Sometimes when I try to kill a buffer containing a LaTeX file, I get this
message:

TeX-clean: Symbol's function definition is void: TeX-active-master

Can anyone please suggest where I should start looking to identify what the
problem is?

I'm using auctex 11.86 on Ubuntu 11.04.

Thanks,
Mandar.