I found this post of yours after replying to your private message. I've moved this to our Snapgear area for better attention by a product expert.
There are a lot of reasons why your SG560 could be running slow. The fastest way to get an answer would be to contact Support and supply them with a Technical Support Report (which you can generate from the SG560 management console). This will let them know exactly how the SG560 is configured.
I'm also having this issue. I tried upgrading to v4 firmware 2 years ago and it did the same thing then. I would really like some help with this issue.
What speeds are expected ?
What speed is obtained ?
As Rick mentioned above, there are many reasons this could be a problem, and it really needs a close inspection by tech support to get the full diagnostics which are not appropiate for posting in a public forum