today saurik put out a cydia update fixing a major bug in the last update. i noticed that when i went to do the upgrade my cydia her is a quick little tutorial for people who are stumped by this issue

when cydia first loads you will have noticed that you cant do anything during reloading data

then there is a very short period when it fetches release data that you will be able to move around... this is the time when you need to go straight to changes and cycle through the update process. if you manage to get the installer running it will be okay and will not crash, but if you dont get to it fast enough it will reload data again and crash

tip: if you have blazing fast wifi i suggest going on 3g to make the process run slower allowing you more time to accomplish this