as i agree with rdl (you should try on another computer if you got one) i'd like to offer you another lead
Had same problem few days ago, lots of corrupted rar and par files
But the guilt was on my usenet provider (astraweb), it did last couple of days, happens sometimes, often linked with lower d/l speeds.
Did you try an alternate (free) server, just for testing?
Or i see newsrazor got us and eu servers, try to switch for testing purpose, with or without SSL maybe?