This really doesn't make any sense to me....I've gone through over a dozen devices and have never experienced anything like this. Internet connection and SD cards have absolutely nothing in common. One should not affect the other....
Drag and drop works, just like any other removable storage. To my knowledge, transferring a different way wouldn't do any good.
My only other guess is that this is a device specific problem. I've never used Huawei (and never will), so I don't know for sure. There may be some odd code Huawei built in which doesn't interact well with SD cards.
Other than that, i have no clue. This is certainly not a core Android problem. All I can suggest is wipe and start over.
The Commandments of Android
1) Open RAM is wasted RAM - Don't use Task Killers
2) Cheap devices are cheap for a reason. Don't expect high end performance.
3) Boot Loop = Wipe.
4) There are no viruses for android.