You can check the installer logs for the MECM client. The logs are located at C:\Windows\ccmsetup\Logs. The main log to check is ccmsetup.log. The log can be viewed using the CMTrace.exe which is located in the following places:
You can uninstall the MECM/SCCM client by running:
Wait a few minutes and the restart the machine. The client will automatically reinstall itself at startup.
Occasionally, unjoining the computer from the domain and rejoining it will resolve issues. You may need to delete the computer object from the domain using the AD Users and Computer mmc snap-in if you don't have permissions to the computer object already and then recreate the computer object.
The client logs are located here:
These can be used to determine why a application deployment may have failed. The main log to examine for application deployments is AppEnforce.log.