Mobile data 2G/3G not working on Tab 10.1 but it works on my other Phone...

I have a Galaxy Tab 10.1 which only has 3G and no calling. I also have a Vodafone SIM which has data enabled and calls/sms too. This vodafone SIM works perfectly on my other phone with 3G and everything else. But it doesn't work on the Tab. My Tab has Honeycomb OS. I tried resetting the APN settings... But no luck. Data and Data Roaming are enabled. On the status bar it says no internet connection. Only once did the data work-only once. Please help me. :confused:

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