This is a frequent error among most of Android phones that were released. "Error 492" usually appears when you try to download an application from the Market, and there is an error with .android_secure directory or with the Dalvik and phone's cache. In both cases, a good approach to the problem resides in the fact that you will need to follow some steps to obtain the good functionality of the Market.
Please try these guides how to perform maintenance on your phone.
- SD-CARD: many users fixed their problem by formatting their card. You can do this by going into Settings > Storage > Erase SD card. A reboot is required after this operation.
- Phone/Dalvik cache: reboot your phone into the Recovery menu and wipe phone's cache and then dalvik cache from the advanced menu. (A ClockWorkmod recovery menu has to be installed for this kind of job).
- Data formatting: from the same Recovery menu, please select wipe data option and then reset your phone.
As you can see, these operations require that you go into Recovery menu. Please note that ClockWorkmod is installed with 3rd-party flashing applications and in most of the cases, performing the flash will void your warranty.