[texhax] Incompatibe list can't be unboxed

[László Kálmán]

Dear all,

Can anyone tell me what this error message means?  I searched the web for  
an answer, but couldn't find information on it.  I get this message from a  
TeX file that I generate with a tree drawing preprocessor that I wrote  
(which uses pstricks), in the context of  
\halign{\hfil#\hfil\cr\rnode{...}{...}\cr...}.

Thanx for any additional info -- LK
-- 
Laszlo Kalman              Theoretical Linguistics Program,
kalman at nytud.hu            Budapest University (ELTE)
                            Research Institute for Linguistics, Room 209
                            P.O. Box 701/518, 1399 Budapest, Hungary
                            (+36-1) 351 4830 x148, fax: (+36-1) 322 9297
http://budling.nytud.hu/~kalman
"Me die?  That'll be the last thing I do!"