Help [Help] Mobile Internet Not Working for Applications.

[Sid.]

I am using LG Optimus One(running on v2.3.3 currently) for over 6 months now and suddenly this weird problem occurs.

I am unable to access to internet on applications via mobile internet.Even Android Market isn't working!

The internet is working only with the stock android browser.

+ My phone is giving me google sign-in error. My phone is not signed into google and when I enter the password it says "network problem".

I am facing this problem ever since I changed the SIM on my mobile phone! (I changed it only for a couple of hours and then inserted my old SIM back).

 

[Sid.]

P.S. I don't have a wifi connection at home. All I rely is on my 3G mobile network.

 

[Sid.]

Please folks help me out.

 

[Sid.]

I realized I posted the query in the wrong forum.
Sorry for that. Please move it to the appropriate section