If after untethered jailbroke your iOS 5.0.1 device using Redsn0w 0.9.10b1 you find the white Cydia icon, then there is a fix for that, simply follow these steps:
1. Turn off and then turn it on your device.
2. Launch Cydia, then install and uninstall any package.
3. Relaunch Redsn0w.
And another solution if the above failed:
OPEN cydia and wait for it to load,
After initiating that you press MANAGE>EDIT>ADD>apt.saurik.com/cydia