Can someone help me please. I'm not super tech savvy.

I've trying to access my NXT wallet for a couple of weeks to no avail. Before logging into my account I get the following message...

A new version of the Nxt client is available (1.2.6). Would you like to update?

When I click OK, I get this message. The hash of the downloaded update does not equal the one supplied by the blockchain. Aborting update.

Then if I log in it just downloads the block chain for hours without me being able to do anything within the wallet. 

Anyone else having this problem?  Thanks in advance for any help.