S3 Upload with pycurl interrupts

Since you mentioned that you experience the problem on Windows 7, can you run a command prompt as administrator and post the results of netsh int tcp show global? You should see something like the following:

TCP Global Parameters----------------------------------------------Receive-Side Scaling State          : enabledChimney Offload State               : automaticNetDMA State                        : enabledDirect Cache Acess (DCA)            : disabledReceive Window Auto-Tuning Level    : normalAdd-On Congestion Control Provider  : noneECN Capability                      : disabledRFC 1323 Timestamps                 : disabled

I suggest you copy/paste the results to a .txt file to make note of your current settings. The settings you are interested in are Chimney Offload, Receive-Side Scaling (RSS), and NetDMA. These are all features that attempt to offload processing from/to the NIC or CPU, and they can sometimes cause problems with symptoms similar to those that you described.

Before messing with RSS or NetDMA, I would try disabling Chimney Offload by running netsh int tcp set global chimney=disabled and disabling TCP offload under Device Manager > Network Adapters > Advanced tab.

If that doesn't solve your problem, you may need to experiment with the other two options. Here is a Microsoft KB article with details on modifying all of them.