Renauld,
I think I had the similar problem: I could not add MM DevExpress controls to my toolbox.
The following Kevin's suggestion fixed the problem:

Generate a new signed key pair for the MM .NET DevExpress Controls assembly. In a DOS window, execute the VS .NET Tool “sn.exe” which may be in one of the following directories on your development machine:

C:\Program Files\Microsoft Visual Studio .NET 2003\SDK\v1.1\Bin
C:\Program Files\Microsoft Visual Studio .NET\FrameworkSDK\Bin

From within the DOS window, change to the MM .NET DevExpress Controls Solution’s obj\debug directory. When your run sn.exe, pass “keyPair.snk” as the name of the key pair file you want to generate. For example:

C:\Program Files\Microsoft Visual Studio .NET 2003\SDK\v1.1\Bin\sn –k keyPair.snk

2. Open the MM .NET DevExpress Controls solution and build it. The new DLL will be in the project folder under bin\debug.

3. Copy the file from bin\debug to the DevExpress Controls project’s root directory, overwriting the existing dll.

4. From within Windows Explorer, drag and drop the new DLL from the bin\debug folder into your Windows\Assembly folder (or WINNT\Assembly). This updates the GAC.

Slava

>Installing Mere Mortals Framework DevExpress Controls.dll and keep getting the following message:
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>The assembly 'C:\Program Files\Mere Mortals .Net Framework 2003\Third Party Components\DevExpress Controls\Mere Mortals Framework DevExpress Controls.dll' could not be loaded. Check that any dependencies the file requires are installed.
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>Any suggestion to resolve this problem.
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>Thanks.
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>
>Renauld