Thanks for reporting this bug it helps us make the software more robust. When Excel starts up it triggers the XLC initialisation process. XLC checks to see if a file called XLC.xll is installed if it is not then it tries to install it. It sounds like your machine is not allowing xlc.xll to be installed and generating an error.
I have done a little research into this and it seems that it is machine dependant and may be due to your security settings. Lets not get bogged down in security settings just yet and we can try to install the xlc.xll addin manually. If we achieve this then when XLC initialises it checks that the addin is installed and will not try to re-install this. Hope you are managing to follow this? Cutting to the crunch, follow these instructions:
1) Start Excel (ignore the 'Add Method of AddIns class has failed'
if you get it.
2) Go to Tools>Add-Ins... This displays the Add-ins form and I am guessing that you will not see xlc installed.
3) From the add-ins form select the browse button and navigate to your XLC installation directory (normally this is C:\Program Files\XLC unless you installed it elsewhere). Select the xlc.xll and press 'OK'. This has manually installed xlc.xll
4) Close Excel and restart it again. Hopefully you will not get an error message again.
Let me know how you get on.
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