Hi Andrew, The Mendix applications work fine on windows 7, I work with windows 7 as well. The problem you are experiencing is caused because you are switching between the 2.4.x and the 2.5.x version.
The client has had some structural changes in 2.5.x and because of this change and because all browsers cache parts of the application you can get some strange results.
When you are switch between a 2.4.x and 2.5.x you should always empty your cache, (even if you disabled the cache, you still need to empty it because Firefox and IE still keep on caching a part of the application)
I had no problems with windows 7 with Mendix 2.4.6.
No problems for me also with Windows 7 and 2.4.6
I also had no problems with mx 2.4.x on windows 7. Maybe deleting your cache will help. Try using another browser.