ASA 5505 throttling traffic?

[Service Spring]

We have 110mbps internet service.  When we have the 5505 behind the cable modem, our speed drops to 55mbps or so.  If we remove the 5505, we see the full 100mbps.  I assume the 5505 can handle the speed; if so, what other things should I be looking at?

As an aside, we used to have 50mbps wich worked fine, then the ISP upgraded to 60mbps and the through put dropped to 30mbps  (It always seems to be half)

Thanks

[sean_evershed]

Hi, Do you get any errors on your outside interface when you connect it to the cable modem?

How have you configured this interface? I seem to recall that Cisco recommends that it should be auto-negotiate.

EDIT: This is a useful document to refere to when troubleshooting your problem

https://supportforums.cisco.com/docs/DOC-12439

[Service Spring]

I"m pretty sure it's set to auto-negotiate by default, and I don't remember changing it

As far as the errors, I'm not sure.  The CEO and my boss saw the problem and un-plugged the device to "fix" the problem.  As of right now, the device is not plugged in