Tricky Issue with connecting to Lync server from my desktop lync client 2010

I am facing a tricky situation here,
Firstly i have 3 modes of connecting my laptop to the internet as follows:
1)Using Wi-Fi connection.
2)A physical LAN cable connection
3)An internet data card (A USB data card).

Now, i can comfortably use my Lync using 1st and 2nd mode of connectivity. But i am having a real issue using the 3rd mode of connectivity i.e using internet data card, it just doesn't connect to the Lync server at all, even though i can browse internet very well.
Later i got a workaround to solve this, what i did was, i connect to internet first with 1st and 2nd modes i.e wifi or lan cable and then i also connect to internet using 3rd mode i.e data card.
After this i start my Lync, which  now connects perfectly and then when it is connected and working.
I disconnect my WiFi or LAN cable this causes Lync to restart, but this time it connect within minutes again using internet of my datacard, isn't this Bizarre ??


Now Could someone please help me to connect the Lync just  by using my internet datacard?

Atlast 2 thing which may be of help is :
1)I can easily connect Outlook to the exchange server using my datacard and retrieve my mails.
2)When i connect to internet using my internet datacard, I can still see "Not Connected Symbol"  in my network indicator on my Win7 PC, But i can still Brows internet.

This problem may have something to do with networking, not sure. Please Help me to solve this !!!

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Ambrish