Jeg fandt dette mens jeg søgte efter hvad der er galt med mit program - quote fra denne side:
http://support.microsoft.com/kb/318804"
Global hooks are not supported in the .NET Framework
Except for the WH_KEYBOARD_LL low-level hook and the WH_MOUSE_LL low-level hook, you cannot implement global hooks in the Microsoft .NET Framework. To install a global hook, a hook must have a native DLL export to inject itself in another process that requires a valid, consistent function to call into. This behavior requires a DLL export. The .NET Framework does not support DLL exports. Managed code has no concept of a consistent value for a function pointer because these function pointers are proxies that are built dynamically.
Low-level hook procedures are called on the thread that installed the hook. Low-level hooks do not require that the hook procedure be implemented in a DLL.
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Jeg ved dog ikke helt hvad jeg skal ligge i det, jeg synes det virker lidt tvetydigt når det kommer til hvordan en low level hook skal implementeres.