android app install package invalid error

[equivocates]

I am having a user report the following error when they try to install the android app. I cannot replicate it on my android phone. Any ideas what may be causing it?

After I click Accept & Download, an error box pops out saying "Error" and under that, it says "Package file is invalid." Then there is a button that says ok. I click ok and it goes back to the installation screen and if I try to download again, the same thing happens and It won't allow me to download it.

Someone in my forum suggested clearing the cache, which seems to have worked:

The "Package file is invalid" error usually occurs because your cache doesn't quite have enough space. Try clearing your cache: Settings- Applications- All- Market Clear data(and cache).

I've also heard of this error magically getting fixed when you switch to using your actual carrier service (if you're currently using wifi).