cannot edit the property of a web service access in FP?

Hi,

I've added a web service reference in the catalog.
then I've created a web page where I call this web seervice, all works fine

Now I want to edit the properties of the data source in my page to change a
parametewr sent to the web service and I receive an error when I click
"reconnect"
server error: there is no file with URL 'virtualfolder/myservice.asmx' in
this web
followed by this message:
server error: the file or folder name 'virtualfolder/myservice.asmx?WSDL'
contains invalid characters that are not permitted. Please use a different
name.

any idea?

thanks

Jerome.