Somehow my Quark wallet managed to create an invalid transaction
I didn't dig too deep to find the root of the problem, but found quick and dirty way to get my Quarks back.
1) Backup the wallet.dat
2) Change
else if (strType == "tx")
in file walletdb.cpp to something like
else if (strType == "tx!!!")
3) Recompile
4) Restart wallet executable
Now it "forgets" invalid tx and coins are available again.