I'm experiencing this problem as well, and signs on my side are also pointing to Rocket. Although my case is a little different because I'm not currently experiencing this problem with web2py, but I'm using Rocket by itself to serve a light-weight service using a smaller micro-framework. However, I have experience this in the past with web2py, and I forgot what I did at the time but the problem went away somehow.
Back to the issue at hand. I'm current using Rocket to serve a tiny WSGI app and using bottle.py as the framework, and I've seen large file downloads (100MB+) missing anywhere between 8 to 32 KB, usually 8K. I've tested with serving directly with Rocket and also proxy-ing Rocket behind Nginx. I'm also using SSL when serving directly with Rocket, and Nginx doing the SSL when running behind it. The issue is somewhat intermittent, and for some reason it seems to happen less behind Nginx but still does. I primarily use curl for my testing, and when it does happen curl would get stuck near the very end and times out after a while. I'm running with Rocket 1.2.4, on Ubuntu 10.04. The problem goes away if I change to cherrypy or gevent, which is what leads me to think it might be Rocket. I found this thread when googling to see if anyone else was experiencing this in the web2py community. I'd be happy to help track this down.
