通过IIS访问网站时，报OCIEnvCreate failed with return code -1 but error message text was n

[s100559296]

急！！！！！！通过iis访问本地网站时，在主页输入用户名、密码后点击登陆，出现以下报错。
Server Error in '/' Application.
OCIEnvCreate failed with return code -1 but error message text was not available.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Exception: OCIEnvCreate failed with return code -1 but error message text was not available.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
操作系统为server 2008 x64 ，ASP.NET服务已开，PLSQL可以正常连接，使用的是ASP.NET v4.0 Classic模式
试了很多网上的方法，都没解决。