streaming videos issue over bis/cannot play streaming vids

Hi everyone I am having a curve 8520 os 5.0 and a BIS data plan and when I try to play any streaming video over youtube it gives me an error CANNOT FIND WEB ADDRESS VERIFY THAT THE WEB ADDrESS IS VALID
I have tried diffrent videos and diffrent websites it works well over wifi but gives me an error over BIS I also called up my service provider they said everything is working fine
I also tried deleting two service books (web browser config) and (Vodafone live) please can any one help me plz
Thanks in advance

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