Greetings!
Thank you for the reports about this. There are several threads going about this and I wanted to take a moment to confirm that a new issue did pop up with patch 2.5.2 that affects many quests that involve clicking game objects to complete an objective. This issue prevents those objectives from being properly credited towards quest completion.
To resolve this, we are preparing a hotfix that we hope to have out very soon that should resolve many of the high-traffic quests in Burning Crusade content that we know are affected, but will not resolve every instance of this issue.
Following this, we are preparing another, larger systemic hotfix which we plan to apply with server restarts in the early morning tomorrow that should resolve any other remaining quest issues.
We sincerely apologize for the inconveneince, and we appreciate your patience as we work through this issue.
Thank you!