in http://code.google.com/p/xrnx/source/browse/trunk/Documentation/Renoise.Song.API.lua on line 2103 I think there’s an abrupt end. My guess is that it should be something like “lines * 256”?
and see 2132 too; it’s about patterns length * 256 
edit
MY BAD mkay, ?
even though length = patternlines*256, you have to convert time values to lines+(delayvalue/256) for the other functions.