st: xtmixed broken in Stata 9.1?

["Dr. Stephen Rothenberg" <srothenberg@mda.cinvestav.mx>]

Dear Stata folk:

I'm trying to run -xtmixed- in Stata 9.1 SE, Windows XP, after successfully 
using it in Stata 9.0.

I keep getting the same error message no matter what my model specs are (see 
below).  Finally I tried copying Example 1 from the -xtmixed- section of the 
panel data manual.

I downloaded the "pig" data set used in the example and tried the code 
listed there:

   . use http://www.stata-press.com/data/r9/pig
   (Longitudinal analysis of pig weights)

   . xtmixed weight week || id:
   last estimates not found
   r(301);

The "not found" error message is the same problem when I use my own data 
set.

Am I doing something dumb or is -xtmixed- broked in Stata 9.1?

Many thanks,
Steve Rothenberg
CINVESTAV-Merida
Merida, Yucatan, Mexico 

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