Yes, I've noticed that too but thought it was simply how the GUI was updating the counts.
I've only earned one lot of interest (0.09...woohoo) and only after finding that block did my wallet update the Staking count but it did not reduce the Spendable count. Of my original 54,000 coins it now shows 54,000 as Spendable, 1,000 as Staked and a Total of 55,000. Obviously this is not correct as it hasn't taken the 1,000 Staked coins out of the Spendable amount.
You should have a few backups of your wallet.dat. I'd rename your current wallet to something like "wallet(test).dat" and copying over one of your backups. I'd like to see the outcome.
Will try this tonight when I get home and let you know the result.