I have a smart bro mobile wifi LTE and I've been encountering this issue and finally able to solve it. I think that win 8 store has issues downloading directly using mobile 3g/4g connection.
I successfully installed and update apps when using the proxy server of smartbro. Apparently, this is a more stable connection since the server caches the data first and doesnt need to do a lot of hops to retrieve the data.
- 121.1.3.200
- 121.1.3.194
- proxy.smartbro.net
- smtp.smartbroadband.
all port 8080