after importing some certificates to the keystore, I can't import any further certificates ("file cannot be opened") or open the certificate manager (it quits immediately without any error message). The same happens when I press the "options" softkey in the EAP tab of EAP-PEAP settings of the EAP connection settings, so I think the keystore is corrupt.

Is there any way to reset it to the installation default without formatting the whole phone? Which tool can access the certificate file?