RefTeX cite problem

[Mathias Lindner]

Hi

I use Emacs with AucTeX and RefTeX and I have a little problem to 
include a \cite macro.
By pressing "C-c [" I enter the regexp and a list of all matching bib 
entries is shown. If I select one with RET nothing happens and the 
minibuffer shows: "reftex-citation: Symbol's value as variable is void: 
reftex-cite-prompt-optional-args".
Yesterday everything worked fine.
Any ideas where to look and what to do?

Thanks a lot!
Mathias