Steps to update extension in Joomla 2.5 extension

Step 1: Login to admin area

Step 2: Go to Extensions and then Extension Manager.

Step 3: Select Update option

Step 4: Prior to clicking on the Find Updates button press the Purge Cache button.

Step 5: This will clear the cached data about the installed extensions. Then you can find the up-to-date information regarding the extensions that should be upgraded.