If you've been in your routers Web configuration screen - you should have noticed the NAT configuration. In the NAT config you'll notice the 'Special Applications' screen. In this section you can configure the router to support multiple connections for these types of applications.
For ICQ try this:
Enter 5190 in the first box next to Trigger Port.
Select TCP for trigger type.
Enter 20000-20019 for Public Ports.
Select TCP for Public Type.
As for FlashFXP - I'll bet the ftp's you visit have more than one default port. Not using much of the default 21 are ya? :p.
http://www.flashfxp.com/images/scr/f-pref1x5.png
Turn off Passive.
Limit local port range to 50000-50100
Forward the ports in 2) to the client PC.
Bind local ports to your WAN IP.
Let us know how that works.