I can confirm that is a problem with my site as well. I haven't noticed it because I didn't have enough post. I dropped the show X threads per page to a lower number to duplicate your problem.
// Page one should look something like
component/option,com_fireboard/Itemid,121/func,showcat/catid,3/page,1/
// Page 2
component/option,com_fireboard/Itemid,121/func,showcat/catid,3/page,1/
// looks like sef_ext.php is dropping the /page,#/ part.
Sorry, I can't offer any solution (just confirmation of problem). Neat site btw.