|Ok I have finally solved this <and the fix was way too simple>|
All I had to do was set the ports to the speed of 10FDx and enable flow control, and my speed was returned to normal.
By the way for those interested in how my setup is connected see below:
We have a Cisco ONS 15327 Optical Router connecting us to our provider's Fiber SONET Ring.
This is connected via a Cat5e Crossover cable into a HP 3400cl on Port 21
Then Port 1 of the HP 3400cl is Connected to our FireWalls Internet Port via Cat5e Crossover cable (It has a address of 64.xxx.xxx.xxx.)
Then Port 2 of the HP 3400cl is Connected to our VPN Appliance's Internet Port via Cat5e Crossover cable (it has a address of 66.xxx.xxx.xxx)
And all connections are working normally.