Hi Jason, thanks for your answer. I didn't find a solution at the moment but if somebody have a solution, I take it ! :)I finally got my issue resolved. My problem was that the string was too long for a GET. Once I changed to POST it started working.
Because I just put a random signature there, I got a signature invalid error:
HTTP/1.1 401 Forbidden Date: Fri, 12 Mar 2010 22:22:52 GMT P3P: policyref="http://info.yahoo.com/w3c/p3p.xml", CP="CAO DSP COR CUR ADM DEV TAI PSA PSD IVAi IVDi CONi TELo OTPi OUR DELi SAMi OTRi UNRi PUBi IND PHY ONL UNI PUR FIN COM NAV INT DEM CNT STA POL HEA PRE LOC GOV" WWW-Authenticate: OAuth oauth_problem=signature_invalid Connection: close Content-Type: application/x-www-form-urlencoded
If I provide the right signature, then it should return me a valid token. The above example just demonstrates that the URL works.