I think that you'll need to get in touch with support to sort this out.
But you could check your order to see if you ordered and upgrade or a new purchase. The serial numbers for upgrade are different, and require the earlier version on your computer ( or its serial number instead).
If you've oredered an upgrade, check that you're entering the correct serial number. You'll probably be prompted to enter both: once for qualifying product and once for the new upgrade.
Let us know if this was the issue. If not, I suggest that you get in touch with Adobe Support.
thank You Vikrant Rai. It turned out to be very simple - before i had the full version (i bought cs6 in Polish) I installed the trial in english so while upgrading it to the full version (after getting my serial via email from adobe) i didn't know that i have to install it once again in Polish. By the way - It would be VERY HELPFUL if adobe users could change the programme language AFTER INSTALLATION. i made a mistake with buying the Polish version and now I have to use it for the next couple of years (I'm way more familliar with my programmes in english :] ).
THANK YOU SO MUCH!!!! I sent an e-mail to Adobe. Let's see what happens :] You are a great helper here Vikrant Rai.