Thought that crossed my mind when i get: Either the file could not be uploaded, or this is not a valid Customization file

From time to time i have experienced that importing customizations from one Microsoft Dynamics CRM 4.0 environment to another like from live to development, might cause problems.
For a long time i have been convinced that the issue were caused by missing RoolUps, moving accross native language for CRM installation.
Now, all blogposts i have found on this issue has different approaches to solving the issue. Some has success by increasing filesizelimit in web.config. Others clean up attributes that with no reasonable explanation are missing in schema but still represented on form objects or in views throughout the application. Others again faces oconflict between versions of Rollups.
Latest i read this thread.

Well, now i am convinced that the issue is far more simple than that.

Removing any tags from exported xml file regarding custom entities that define any custom icons make all my previous attempts on different organizations work!

So xml file is just a noline textstring seperated with tags. could it be that that string is missread by the parser on import, and that the mistake is that it is limited by the lenght of some types of tags?

Hope that this will be solved in a future roolup for Microsoft Dynamics CRM 4.0.