Why does cydia work one day but not the next?

I recently wanted to try jailbraking but there's none for ios 7 for iphone 5 yet. Instead I downloaded green poison 5.1.1 for my second generation ipod yesterday. Everything was going fine. Downloads and upgrades were fast. Then I went to delete itransmission 2 because it didn't work right. Cydia told me it would be unsafe to do so but I did it anyway. After that cydia disappeared so i guessed I made a mistake and restored the ipod and did the jailbreak again. Cydia is installed but when I try to do the 6 upgrades or downloads anything else it is really slow and gives me hash sum mixmatch and posix timeout errors on everything. I refreshed cydia every time, rebooted my ipod but it still won't work. What could be wrong?

Added (1). The only Evasi0n I know of that is real supports 6.0-6.1.2. I have 5.1.1.

Download Evasi0n instead. It has less bugs.