Hotline has a screwy k/sec calculator. Hence the reason that when you resume a download, it usually goes really fast for a few seconds then drops.
If the same thing is happening when you begin a transfer, then it might just be the server. Does that happen with all the servers you go to? Try going to hltracker.com and downloading something there, see if it happens there.
If it doesn't, then it's something to do with the server's connections or your connection to your ISP (neither of which you can help).