Why does my wallet balance show different to the balance of the wallet address in the darkcoin explorer?
Your wallet holds keys to a number of addresses not just 1. Your wallet may have say, 100 DRK in it, but that may be 25 in address A, 60 in address B, and 15 in address C. When you go to look up what you think is your "wallet" address, it is just 1 of those addresses so you may only see 25 DRK in the explorer.
Someone else can chime in as to how to check all the addresses in your wallet.