an error has occurred on server

Hi all,

I have a scenario i am creating a webapplication in moss 2007,for this what i am doing is using the existing site in moss 2007,so for this i created a site template of the existing site and adding the visual studio code to my new site.for this i am adding the .dll file in bin directory of the webapplication(here we are not having the option of deploy the visual studion solution).so we created the solution for the VS and deploy the solution in central admin.after adding all this when i am trying to add the web parts i am getting the error

"An error has occured on the server" 

i dont know how to come out of this

please any one suggest me

Ramu