Crash on start (Can not find file of assembly System.Core) about bukkitgui2

[Bertware]

Can you specify the contents of the error message?
Also, please make sure you're running a v2.x file if you downloaded a binary (.exe) file.

[yocool13]

The error said:
The application encoutered an unexpected error!
Please contact the developer with the following information:
Exception: Can not find file of assembly System.Core, Version=3.5.5,
Culture=neutral, PublicKeyToken=b77a5c561934e089. The system can not find the requested file.
Details: at Net.Bertware.Bukkitgui2.UI.MainForm..ctor()
at Net.Bertware.Bukkitgui2.uiLauncher..ctor()
at Net.Bertware.Bukkitgui2.Program.Main(string[] argStrings)

[yocool13]

I had to type this over because i could not copy it. and i had to translate it because i and my laptop are Dutch.

[Bertware]

Make sure .NET is installed correctly. Try reinstalling .NET 3.5:
http://www.microsoft.com/en-us/download/details.aspx?id=65

[yocool13]

I installed .NET framework 3.5 and it still gave the same error.

[Bertware]

Hmmm...
"Can not find file of assembly System.Core, Version=3.5.5,"
That line means one of the .NET framework files is missing, try removing .NET entirely (not just reinstall, remove it first and reboot) then installing it again (complete 3.5 installer: http://download.microsoft.com/download/6/0/f/60fc5854-3cb8-4892-b6db-bd4f42510f28/dotnetfx35.exe )
Eventually you could try installing .NET 4.

[yocool13]

It Worked. Thank you verry much