Forum thread link pointing to wrong url
 

One of the therad in my forum is pointing to wrong URL. Thread ahs 4 pages. First page can be accessed, When I click on second page
error message is
Forbidden

You don't have permission to access /showthread.php on this server

it points to link
http://www.mysite.com/showthread.php?2013-GrandMaa-s-Lovely-Secrets..../page2

If I click on link
http://www.mysite.com/showthread.php?2013-GrandMaa-s-Lovely-Secrets/page2

it goes to correct URL

If .... are removed it is pointing to correct URL.
This is only with one thread.
How do I fix this?