These values do seem a little low, which is more likely to be down to your ISP than it is to your settings, however Windows generally is optimised for LAN style networking, rather than internet networking, there are any number of tools out there for optimising DSL connections (google if interested) & while they *can* make a difference my experience is that difference is marginal.
There is a script in the tutorials section for setting WinMX's bandwidth throttles optimally, however it's usually more useful for resolving WinMX slowing other things too much & is really most applicable to users on dial-up, though you may wish to check it out, setting too low values would certainly cause your symptoms.
As far as I'm aware there's no "magic bullet" to resolve this one, unless it is down to your throttles being set too restrictively, & it will otherwise take tedious investigation to isolate the exact cause, which still may not be amenable to resolution.
