Concurrent operations limit in metro app

In my metro application, I am creating some parallel background downloads using

BackgroundDownloader^ downloader = ref new BackgroundDownloader();

Very often, I get an exception at this point which says:

First-chance exception at 0x75424B32 in WWAHost.exe: Microsoft C++ exception: Platform::COMException ^ at memory location 0x03C5E470. HRESULT:0x8000000E A method was called at an unexpected time.

WinRT information: Quota for maximum number of concurrent operations exceeded. Wait for an operation to complete before starting new ones.

If there is a handler for this exception, the program may be safely continued.

I have no clue on this limit and there is no documentation on msdn whatsoever about it. Did somone come across such a situation before? Any ideas are welcome.

A little late on this thread but we used BackgroundDownloader to download 1,000 files at once and it is actually much faster to download them all at once instead of in smaller batches.