Character changes in Explorer Addressbar

Hi,

In the company I work for am I responsable for the webservers and
sites, not the content just the technical part.
Recently we've upgraded all our servers to Windows2003 and it seems to
be working great. Unfortunately when we use hyperlinks to other parts
on our site the address seems to be adjusted.

URL: http://www.mysite.com/my-family is changed into
http://www.mysite.com/my2%Dfamily

All special characters will be replaced with its substitution. But only
when I end the URL with the / (Like http://www.mysite.com/my-family/
) the substitution won't take place.

Could some one explain if this is a client problem (Internet Explorer 6
on WinXP pro systems) or has it something to do with IIS (IIS6 on
Windows2003 servers)

And how can I solve this issue.

Thanx in advance for helping me out with this issue.

Regards,

Jeroen van Hoorn