The search request was unable to connect to the Search Service.

In order to resolve this error "The search request was unable to connect to the Search Service.":
1. Go to the server:
Run > Type “Services.msc” - >
- Start a SharePoint search service;
- Start Indexing service;
- IISReset

Sharepoint Service Error: A deployment or retraction is already under way for the solution *.wsp

Sharepoint Service Error: A deployment or retraction is already under way for the solution *.wsp

To resolve this problem do the next steps:

Click "Start", click "Run" type cmd

The operation below shows you all runnig deploying process:
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\BIN>stsadm -o enumdeployments

Base on GUI of process you can cancel it. Use next operation for that:
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\BIN>stsadm -o canceldeployment -id "GUID job ID"

Security Classes

SPGroup
SPUser
SPRoleAssignment
SPRoleDefinition