When I render the pictures that have been exported from light-room only half the number of images are processed in the final video.
The preview of the render looks fine and all the pictures in the light-room output folder look ok too. 
Is there anything obvious that I am doing wrong.

Regards, Bob

p.s a number of other sequences worked perfectly fine

Please see this faq thread: http://forum.lrtimelapse.com/Thread-rend...e-sequence
Check you log file too (info menu/show log). If you can't get it going, send me the log file.