Unbelievably simple based on the "extra info" you provided.
HTTP_X_FORWARDED_FOR 172.16.231.215 Dubious
Conclusion You are using a transparent proxy: 195.169.155.126
You can't use a transparent proxy for pete sake!!! You should be able to use, depending on the site(s) in question, any high anonymous (elite) proxy that isn't a Planetlab/CoDeeN.
However, your best bet is simply to use either a web proxy or cgi proxy. Search for them using Google's search engine.