I use 2 workbook addins, one .XLA for all my procedures and functions, and one .XLAM for the Ribbon interface.
If I try to run a procedure that is in the .XLA workbook from within the .XLAM workbook, I use the CallByName command.
This generates an "Error 438 : Object doesn't support this property or method"
As documented in the MSDN http://support.microsoft.com/kb/937201 this should only occur when using the vbGet call type.
I get it allways.
Anyone experienced this behaviour too ?
Well, I'm not sure how much help this is, but the mechanism you describe (i.e. using CallByName to access procedures in one Add-In from another Add-In) works in principle. In Excel 2002, that is. I don't think the error you get has anything to do with the hotfix issue you linked to, as that refers only to passing around Chart objects, which is not what you are doing (or is it?)
Obviously, there are a lot of things that can go wrong with CallByName, the simplest being that either the specified object or the specified procedure isn't available. In the latter case, you always get an RTE 438.
The best way to debug this, I'd think, is to wait for the error to occur, then skip that line and put in an explicit call to the specific object procedure (without CallByName) underneath and step through that to see if your syntax is correct...
Other than that, it's hard to diagnose the problem without more information. :-\
The problem arises in the 2007 version.
The 2 addins are an old .XLA type addin for all the general procedures and functions and a new .XLAM type addin for the 2007 ribbon interface callbacks.
The CallByName procedure works ok from the .XLA to the .XLAM.
The error 438 occurs when trying to call a procedure from the .XLAM to the .XLA.
Hope this clarifies the situation a bit.
You might try adding a second XLA and XLAM add-in to test XLA->XLA and XLAM->XLAM calls in your version, maybe that'll shed some more light...