RST, ACK at the beginning?

I'm getting a strange RST, ACK at the beginning of a SOCK transfer.

Client RST, ACK -> Server

1 minute later

Client SYNC -> Server Client SYNC, ACK <- Server Client ACK -> Server Client SOCK -> Server Client SOCK <- Server

It's strange the RST, ACK seems to be in response to a session which completed 10 minutes earlier. Once, the SYNC is sent everything runs fine. I did notice my client sent six duplicate ACKs at the end of the last session which again was 10 minutes earlier.

Thanks in advance.