I am currently running version 8.1 with upgrade 2.

After trying to install upgrade 3 and then rolling back to upgrade 2 i get the error OLE error 80131040 everytime i try to launch a .net extenstion.

I think the problem is that somewhere on my machine it is looking for the new .net frame work dll.  

The version i have in my .net exts is 8.1.0.1146.  

I'm not sure if there is a way to find where it is looking to find a different dll version.

Have you tried running the RegisterSLXNetExtentions.bat located within C:\Program Files (x86)\SalesLogix - There is another thread that reports the same error and running the RegisterSLXNetExtentions.bat resolved the issue.

I have tried that.

I've actually completly uninstalled saleslogix, deleted the saleslogix folder and deleted registry keys and then reinstalled and then run the .bat file and still no luck.

Maybe try opening the source code for the extension, remove and readd the reference to the framework dll, recompile and then update the extension? This way you can be sure it's looking for the framework version that matches the SLX version.

After doing that I can launch the .net exts from another machine looking at the same database so it seems to be something specific to my local environment.