Workflow Errors - Contd

1)
"The security validation for this page is invalid. Click Back in your Web browser, refresh the page, and try your operation again"

Set

SPWebObject.AllowUnsafeUpdates = true;

This should work as a breeze


2)
"New instances of this workflow template are currently disallowed"

This is probably the easiest one:

Go to Doc library settings --> workflow settings--> Remove workflows --> select "Allow New Instances"