First of all, a 1MB connection would mean you'd have a max download of about 125kbps (shown during a download of files via e.g. Firefox).
If your max DL is 1000kbps tho, that'd mean you have a 8MB connection. A download of 50kbps is pretty low for that matter - I myself download at around 500-600kbps when it comes to downloading from the Panzar-Servers.
As far as I understand your post, you have a steady 1mbps download anywhere but Panzar. Do you have any bandwidth-regulating programs installed (such as NetLimiter) and added a limit by accident? And: do you have such a low speed on any PC in your network?