Strange - I was playing with this again tonight on my test forum and when I entered a multi-page thread, jumped to a later page (page 11 in this case) and clicked on Thanks, the URL changed back to the first page of the thread!?
So, e.g. on page 11 of the thread:
http://www.example.com/vb4test/showt...-thread/page11
...the /page11 is stripped off and I'm brought back to the first page. I have the most up-to-date version of this hack installed.