After I updated it to latest revision (3.3.8 ) receiving address changed. Why?
Most likely because the latest version is working "correctly"
The older version *should* have been changing the address as well, but it didn't always work properly... with the newer versions, the wallet will give you the first "unused" receiving address (where tx == 0) that it finds in the list... once it has been "used" (tx >= 1), an address should not automatically show up on the "receive" tab any longer. If it was already on the receive tab and the address receives a transaction, and then you go back to the receive tab, it will be highlighted RED to warn the user that it has already been used. If the wallet is subsequently closed and re-opened, that "used" address will then be skipped and the first unused address in the list will be shown instead.
However, as TryNinja said above... any and ALL of the address(es) shown on the "Addresses" tab will remain valid and can be used at any time.