"If you’ve ever attempted to root a device prone to difficulties or requiring a trial-and-error type exploit (the Motorola Droid X or T-Mobile MyTouch 3G Slide, for example) then you know how easily it can go wrong. Sometimes the operation fails and you end up with the superuser app installed but without actual root file system access. A quick search for ”lost root” on our forums yields an astonishing 274,000 results. Almost all the visible results link to posts where forum members believe they have lost root access, usually due to updating a ROM or accepting an over-the-air update.
XDA Member android_owl has created an app to help out in these all-too-common situations. SU Checker searches for and identifies Superuser binaries on your device in a flash. It can help check for root if you suspect you may have lost permissions. This great little diagnostic tool and time saver can be found in the release thread or on the Android Market here. Give it a try the next time and let the developer know what you think!
" - xda-developers.com 13/02/2012