From Forum Nokia Wiki

A stray-event panic from the Active Scheduler ( E32USER-CBASE 46 error ) is a most common problem with an Active Objects. This is ussually caused by one ( or more ) of the following:

• You forgot to call CActiveScheduler::Add() before starting the Active Object.
• You dont call SetActive() after issuing an async request.
• Passing the same iStatus to two service providers at the same time ( multiple requests outstanding on the same Active Object ).

Do not invoke DoCancel() directly - it should be private - always call Cancel(). Note that Cancel() should be always be called in the destructor of your derived class.

Other related pitfalls (triggering other panics):

• Using your own TRequestStatus variable, instead of using the one provided by CActive.
• Passing automatic variables when doing an asynchronous request.

Careless use of active objects can degrade the response time of UI in case of:

• Priority of active object is higher than it is necessary
• Method RunL() works too long