Some of those who jailbroke 3.0, much like me may have experienced some problerms with Cydia, most of them will be 
small glitches which will be fixed in an update but for some you may have experienced this whilst trying to install Cydia downloads.
Even though if you got this things normally still installed without a problem it was annoying having to go through this everytime you download and install something however there is a fix.
As this seems to only occur when you install All Sources from Steffwiz, uninstall it and the sources will still remain but the problem seems to go away.
Sam's Blog 