Pro connects to 2 extra ultrapeers (people with fast connections to help you search) & also connects to a couple of extra hosts for download (max is 14 for a T3 connection).

Well I'm confused...you said you'd never been able to download movies but you're getting between 1 KB/s & less than 40 KB/s for movie downloads???

What's your connection speed? Do a speed test.
Speedtest.net - The Global Broadband Speed Test

Try downloading a movie from here & see what speeds you get.
Magnetmix

Have a look at the first few posts below for tips about optimising LW's performance.
A few things to consider while configuring Limewire for optimal performance...

Tell us your system details.
System details - help us to help you -> Provide these details when you post!!!(click on link)

Pro isn't going to make any magical difference to downloads if you're already having trouble with basic. Pro might help with more search results & those extra hosts to download from can boost speed a little bit. But in your case I'd say wait until we see if we can help you with basic first