No solution, but more info. Been tracking this problem since jailbreak 4.3.1 using sn0wbreeze on a windows 7 PC. At first it was amazing how much faster Cydia was until it went to fetch the unfetchable packages.gz file. You guys describe the problem exactly as it occurs for me as well - the same four failing repos, the same duplicate sources that cant be edited/removed. One post that I read indicated the where the repo files exist on the phone and instructions for deleting the files. I tried that remedy and no luck so I deleted more files that seemed to be related to the problem...no luck. Whenever I would delete the local repo files on the phone and then lauch Cydia, the folders and files are rebuilt when Cydia is launched. This might imply a problem with the server, but seems like there are not many people reporting a problem with this so I'm thinking it maybe a particular app or phone version. However my gut feeling is that this is a Cydia problem. Hopefully one of us finds the real solution bs we can get back to life.