Category menu non operating in some browsers with Wishlist Member activated

Does anybody have any information why with Wishlist Member activated in some browsers the operation of the category menu selection on the front end do not redirect to the applicable pages when clicked.

IE8 maybe surprisingly, always is OK, Firefox sometimes does and sometimes does NOT work, Chrome has never worked and for no apparent reason or change by me Opera started working yesterday.

A colleague has hinted that some servers have a problem, why?, not clear, however, bizarrely when talking to my hosts tech. support, they tried the actions with IE8 and it did NOT work for them, they did not try the other 3 browsers.

I have contacted Wishlist Products and this was a new problem to them and could not explain the issue.

If anybody has had the same problem with other plug ins the solution may work here, however, the problem hints that it may be a browser related problem.

Thanks in anticipation.