TCP inbound on 192.168.1.12 but outbound on 192.168.1.10 - Huh?

Hi all
Any help would be appreciated on this one
I can RDP to any other server on the 192.168.100.0 subnet except the
RSA box on 192.168.100.18
This is because I have a static route that points 192.168.100.18
255.255.255.255 192.168.1.1 on the RRAS server back thru the DMZ
interface of the PIX (which is 192.168.1.1). This is so all the PPTP
and GRE traffic will go back out the PIX - better for security I
believe
When I try and RDP to the RSA server (192.168.100.18) this is what I
am seeing

pix(config)# sh pdm log | i 3389
6|Mar 08 2007 12:12:10|302013: Built inbound TCP connection 22918639
for dmz1:192.168.101.21/2669 (192.168.101.21/2669) to inside:
192.168.100.18/3389 (192.168.100.18/3389)
6|Mar 08 2007 12:12:18|302013: Built outbound TCP connection 22918648
for dmz1:192.168.1.10/3389 (192.168.1.10/3389) to inside:
192.168.100.18/2301 (192.168.100.18/2301)
6|Mar 08 2007 12:12:18|302014: Teardown TCP connection 22918648 for
dmz1:192.168.1.10/3389 to inside:192.168.100.18/2301 duration 0:00:00
bytes 0 TCP Reset-O

192.168.101.21 is the IP assigned to my PPTP connection
You can see it build the inbound connection correctly but for some
reason the outbound is going to another server on the DMZ

Do you know of any reason why this is occuring? I want to also setup
the same thing for HTTPS to work.

Thanks in advance

Scott