I am not sure when an upload fails, but it did appear to seem excessive:
Things have gotten a little smoother when I change my connection setting to allow one more client, my connection settings are:
0K download
12K upload
3K slots
before I had 4K slots.
here are my stats now:
total successful uploads 538
total failed uploads: 393
FYI... I have a 300K line... The upload is greater than the average 128K but not much. For example i able to get up to 17K-18K max on uploads, which is why I choose 12K instead of 10K.