If you have installed something and need to uninstall it without losing your jailbreak/can't get into your phone to do a traditional uninstall, you can always do the following:
Download/Install iFunbox
http://ifunboxmac.com/
Plug in your phone via USB and open up the SSH Terminal Window
You need to know the package name that you installed "com.XXX.xXX" and run the following command:
apt-get --purge remove (source name)
then type in "reboot" in the command line to reboot the phone
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Now if you want to reinstall Cydia without re-Jailbreaking this can be done also, not sure of your knowledge level regarding Jailbreaking etc, I had some trouble on my end but had a package jack up my phone and was able to fix it by manually removing the package and reinstalling Cydia. I do have some issues with my iMessages and Facetime after the fact, but I never use those anyway, so I can live without it until the 5.1 jaibreak comes out.