I was getting this error today whilst trying to import my solution
Error while Importing a solution in CRM 2011 – The solution file is invalid. The compressed file must contain the following files at its root: solution.xml, customizations.xml, and [Content_Types].xml
after about an hour of frustration the solution to the not importing solution finally struck me.
The problem was I was zipping up the solution folder, this then creates a zip file with a folder at the root and then the three solution files
Hosk Solution
[Content Types].xml
solution.xml
customizations.xml
What you have to do is select the three xml files and then zip them up. This then doesn’t create the root folder.
This is definitely a “Monday Morning” error and it’s a pity CRM doesn’t have an root folder error which I’m guessing would save a lot of people a frustrating hour or so.