Do you have a NAT pool configured for you users to go out as? Do you have configured which internal subnets can use this external NAT pool?
Here are some samples:
Assigning the NAT pool:
global (outside) 1 207.1.1.1-207.1.1.253 netmask 255.255.255.0
global (outside) 1 207.1.1.254 netmask 255.255.255.0
(We've assigned a full class C subnet to our external NAT pool. The last address is listed singularly, so that when all 253 addresses are in use, the final 254th address uses NAT overload, aka PAT and 65335 - 1024 PATs may take place).
Next, you must specify which internal subnets may use your NAT pools:
nat (inside) 1 10.1.1.0 255.255.255.0 0 0
nat (inside) 1 192.168.0.0 255.255.0.0 0 0
You also need to have a default route configured on the outside interface, and routes to all of your inside networks configured (inside gateway is 192.168.2.1):
route outside 0.0.0.0 0.0.0.0 206.1.1.1 1
route inside 10.1.1.0 255.255.255.0 192.168.2.1 1
route inside 192.168.0.0 255.255.0.0 192.168.2.1 1
Test connectivity on both sides with the ping inside/outside command, and view open NATs with 'show xlate'.
Cisco TAC has a huge list of sample configuration for this and more, including PIX to Router VPN configurations:
In fact I just spotted a brand new article on how to make a PIX work with PPTP on Win32 platforms: