I am using HTK 3.4.1 in Ubuntu 12.04. I followed the guide in Vox Forge. However I got this error in re-aligning:

  ERROR [+8522]  LatFromPaths: Align have dur<=0
 FATAL ERROR - Terminating program HVite

I searched with google and found some explaination like

"

'sp' is a tee model in the aligner, which is used to handle possible
between-word pauses. It may have a zero duration. The tee model doesn't work
under htk3.4.1 when doing alignment (Align have dur<=0), but 3.4 works.
align.py inserts 'sp' between words before doing alignment, that may be why
sometimes you'll see an error but sometimes not when using 3.4.1. Also, if the
transcription words are very different from what's in the speech, the aligner
will also report an error, meaning that it cannot find boundaries
"confidently".

"

from http://harris.sas.upenn.edu/pipermail/splunch/2010-April/000244.html

and related explaination for this error here (http://www.ee.uwa.edu.au/~roberto/research/speech/local/entropic/HAPIBook/node276.html) says:

"Lattice structure invalid

The lattice was incorrectly formed. Ensure that the lattice was created properly."

Does anyone have similar experience?