I've been testing out a SMC TigerSwitch 8612T (same as a Dell 5212, managed layer 2 switch) and encountered something I'd seen before, but only in cheap, junky switches: it seems to hate 10baseT equipment. It will negotiate the proper speed, and the link comes up, but packet loss is extremely high. I've verified that it isn't anything else in the stack by plugging into my main switch, a 24-port Black Box managed switch.
I know other people have run into this before, but I've never heard a real explanation for it. I've got a bit of 10baseT gear (JetDirect card in my old LaserJet 4, Digium IAXy ATAs, old utility PC), so it's important to have backwards compatibility...especially when the product is advertised as being backwards-compatible. Does anyone know why this happens?