Redirect_to problem - not redirecting


I have an application which is to talk to the protx VSP server system.
In order for it to work I need to redirect to a url which looks like the
following :{88F1532E3-17E8-410A-A688-1E1ABCDDD50}
(the above is not a valid transaction id just an example)
this is stored in a variable called next_url

so when I call redirect_to(next_url) the system does not redirect me…
I get a blank page instead.

if I remove the curly brackets bit then it does redirect, but protx
needs the curlies. Seems like it is having problems with the curly
brackets in the string

Any ideas