Was it the poor sales of the Flyer or the company's desire to use Sense UI that caused Microsoft to refuse HTC a Windows RT licence?
Hopes that Microsoft's Windows RT - the operating system previously known as Windows 8 for ARM - would be a brave new frontier for the mobile-centric architecture are looking shaky, with smartphone giant HTC finding itself locked out of the platform for having the temerity to want to customise the user experience.
HTC's current crop of devices, which include smartphones and tablets, use a unified user interface developed by the company called Sense UI. This user interface makes HTC's devices stand out from the crowd, and is a technique used by many manufacturers: Samsung's popular Galaxy product range, for example, uses a customised user interface known as TouchWiz.
HTC had planned to create a Windows RT tablet which would include a customised home screen designed to be instantly familiar to anyone who had used a Sense UI-based device in the past. So far, so regular.
Microsoft's response, however, is ever-so-slightly irregular: the company has cut HTC off from Windows RT entirely, refusing to allow it to launch a device based on the operating system at all.
The decision to cut HTC out of the market is a surprising one, given the companies' long history: Microsoft and HTC worked closely together on what was known as Windows Mobile, with HTC launching the first Windows Mobile smartphone at a time when the company was unknown other than as an original design manufacturer (ODM) for other brands.
The partnership proved profitable for both: with HTC's help, Microsoft saw Windows Mobile become a major player in the smartphone market; with Windows Mobile as a near-unique selling point, HTC in turn became a household name to rival Nokia and Samsung.
By cutting the company out of Windows RT development in this manner, Microsoft is sending a clear signal: Windows RT devices will follow the Microsoft-mandated guidelines, or they won't exist at all.
There are hints, however, that Microsoft had other concerns about HTC's involvement aside from its desire for customisation: Bloomberg
quotes unnamed sources familiar with the deal as stating that Microsoft based its decision on concerns that HTC is a relative newcomer to the tablet game - having launched its first tablet device, the Android-based HTC Flyer, in May last year - and doesn't sell enough devices in general.
That's a handy excuse - and could even ring true, thanks to poor sales of the surprisingly expensive Flyer - but HTC's latest financial guidance still claims it will clear almost £2 billion in sales for the second quarter of the year, while its latest HTC One X handset is proving a popular alternative to Samsung's Galaxy S3.
HTC may be permitted to produce a Windows RT product in the second wave, but it won't be there at launch - and with sources claiming that just five devices will be available at release
it's looking increasingly like Windows RT is going to prove little threat to the existing tablet market.