The "Message" task was not found

Suddenly when I opened by Visual Studio 2008 solut开发者_如何学编程ion today and tried to rebuild all, I got the following error:

The "Message" task was not found. Check the following: 1.) The name of the task in the project file is the same as the name of the task class. 2.) The task class is "public" and implements the Microsoft.Build.Framework.ITask interface. 3.) The task is correctly declared with in the project file, or in the *.tasks files located in the "D:\WINDOWS\Microsoft.NET\Framework\v3.5" directory

I don't understand anything of this. Can you please guide.

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I restarted my computer and the error disappeared :)

Updated:

Based on the below comments (Thanks to @Thomas & @Vikram), it seems that restarting Visual Studio also fixes the issue.

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I had the same problem in VS 2013 and fixed it by cleaning the solution.

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Just right click on the offending project and select "Clean". It's a bit faster than restarting VS. I still don't know what is causing this issue for me but that fixes it so that I can build the project.