Cydia not working need help please!!!!!?

I jailbroke my iPod touch 3G 8gb 4.2.1 with greenpoison and I was downloading stuff when it just crashed, when I downloaded nocyrefresh Cydia immediately started to crash upon startup so I tried to rejailbreak my iPod and it still didnt work, so I went on the Internet and researched it so I download iphonebrowser on the computer and manually deleted all of my uploaded sources like it said and when I went to reboot it it kept on doing the spinny thing so I held the lock and home button for 30 sec. It restarted then said connect to iTunes so I did and I had to restore my iPod, I was mad, but I still jailbroke it again with greenpoison, but when I installed Cydia again from loader and rebooted my iPod it was there the i loaded it and it said something like loading or installing or somethn like that, and a spinny thing then it went to my lockscreen so i tried again and it still does it, what do I do??? Please help!!!!