Sometimes 3rd Party apps are not written cleanly or updates are not clean, sometimes the OS itself is not able to manage partial / incorrect installs, upgrades or uninstalls, and sometimes you don't even know the reason why this happens!
But yes, its a very real problem for BlackBerry owners. A sample post discussing the same - Cannot Uninstall/Delete certain software!!
To this end we did some research on it and have released the industry's first 'universal uninstaller' - Mobylo! SureWipe. The basic idea is that a BlackBerry owner should be able to try all the worlds shareware, demos and trials without
having to worry about how to uninstall them later.
For your reference, here are some BBF Pages discussing the same. (A search for Surewipe will give you more) : Uninstalling yahoo messenger/ needs help
And, this is the official page for SureWipe: http://www.mobylo.com - Mobylo! SureWipe
Please feel free to follow up with any queries, we will be glad to assist you!