Am trying to import a private key in the windows client version 1.5.1.0 with 5 connected nodes and up to date blockchain (i believe)

I keep receiving this error when I attempt to importprivkey in debug window;

"Error adding key to wallet (code -4)"

When I look at my receiving addresses it is showing up their, but it doesn't reflect a change in my balance.
Not sure why it isn't accepting it.. When I search the public address on the blockchain it shows an accurate balance.. Any suggestions would be appreciated. Thanks.

Message Me. aseriousgogetta@[g]mail.com