The last entry on the MediaMax blog dates from march 6, but that problem was solved even though their blog hasn't been updated to reflect that. However, since the last 2 days it has reared it's ugly head again. For the last 2 days hardly any uploads will show up in your account and for the very few uploads that do there isn't any pattern noticeable. Don't bother re-uploading the file either as experience has shown it will not improve your chance of seeing it popup in your account so we can only sit tight, wait, and hope MediaMax figures out where our uploads go and can fix it without having us to re-upload all files that haven't shown up so far.
We're also, again, at countdown for V6 beta testing which should start the 15th if memory serves ... if it's not postponed again that is.