"Failed to sign transaction"?

Trying to send coins from t to z-addr ... had no problems in the past, but i got this today:

[
{
"id" : "opid-8d2b7b75-38bf-4d77-a0b6-7695b3fedfcc",
"status" : "failed",
"creation_time" : 1481144173,
"error" : {
"code" : -16,
"message" : "Failed to sign transaction"
}
}
]

?

I have the same problem.