The way I have my network setup at home is as follows:

 

Cable Modem> Gigabit Router> Powerline Adapter A> Powerline Adapter B> Gigabit switch> Laptops

 

I have an Unraid server hooked directly to the router and it stores all of my files. What I'm trying to accomplish is allow my two laptops upstairs access to the server. When I hook up my laptop directly to the router, I get transfer rates of about 60mb/s. However, when I go through the switch I only get around 6mb/s if I'm lucky. At first I thought it was the powerline adapter, but when I removed the switch out of the equation and hooked a laptop straight to the powerline adapter, I get transfer rates of 60mb/s. I've tried two switches (although both are from the same mfg) but get the same results. I've even tried bypassing the powerline adapters competely and hooking the switch straight into the router with the same results.

 

Switches in question are: TRENDNET TEG-S80G and TRENDNET TEG-S50g

That is odd.  I think you'll just have to consider both switches defective and seek warranty replacements.  Did you have a power surge recently that could have fried them?  Are they plugged into surge protectors?

 

I use the TRENDNET TEG-S80G and the cheaper 5 port model (with the plastic housing) and both work great, no slow downs at all.

 

Finally, are you sure the laptops aren't connected by wireless?  I only ask because 6 mb/s is about the speed you can expect to see over wireless.

That is odd.  I think you'll just have to consider both switches defective and seek warranty replacements.  Did you have a power surge recently that could have fried them?  Are they plugged into surge protectors?

 

I use the TRENDNET TEG-S80G and the cheaper 5 port model (with the plastic housing) and both work great, no slow downs at all.

 

Finally, are you sure the laptops aren't connected by wireless?  I only ask because 6 mb/s is about the speed you can expect to see over wireless.

No power surge and both are always plugged into surge protectors. I've even tried disabling wireless on my laptop but to no avail.