Private key for is not known (code -4)

[testz]

I just want to get my Private key for pts but i got the message:
Private key for address myadress is not known (code -4)

i tried with the debug window
dumpprivkey Pmyadress
what can this mean?
is it because i have set a password?

Here? https://bitcointalk.org/index.php?topic=325261.msg8502306#msg8502306

[bitmeat]

You are using a BTC privkey instead of PTS

[Reiner]

I just want to get my Private key for pts but i got the message:
Private key for address myadress is not known (code -4)

i tried with the debug window
dumpprivkey Pmyadress
what can this mean?
is it because i have set a password?