I did not write for a while, but it does not mean I quit SharePoint war, oh, no. I am still in first line.
Today is a good one.
When I edit page I get:
The URL 'Pages/Page.aspx' is invalid. It may refer to a nonexistent file or folder, or refer to a valid file or folder that is not in the current Web.
When i try to check out, I get same error.
Well, don’t panic ,check your ULS log.
You may find that
System.Data.SqlClient.SqlException: The transaction log for database 'SharePoint_Config' is full.
You look on you DB server and your disk has ZERO disk space left.
Here you go, another cause of this error (you may find more). This is probably the easiest one.