Microsoft's 128GB Surface Pro tablet sold out online within hours of going on sale in the US on February 9.

Shoppers for the $1,000 tablet at the online outlets of Best Buy and Staples, as well as Microsoft's own web store, began seeing "not available" or "out of stock" notices just hours after midnight Eastern Time when the Windows 8 slate went on sale.

Although the 128GB edition of the Surface Pro has sold out online, that's not the case with its $899 sibling, which has 64GB of solid state storage.

Surface Pro 64GB sales may be suffering from criticism it has received for the actual amount of storage space it provides for user content. Of the 64GB of space on its SSD, only 23GB (36%) is available to a user. By contrast, the 128GB Surface Pro has 83GB available to users, or 65% of the drive.

Microsoft has been a little slippery on the actual amount of space available on the slates. Just before the tablets went on sale, Redmond recanted its initial numbers and bumped up the available space on the 64GB Surface Pro to 29GB and on its bigger sibling to 89GB.

As news of the Surface shortages spread, Microsoft issued a statement to the press:

"Customer response to the launch of Surface Pro has been amazing. The Microsoft Online Store is currently out of stock of the Surface Pro. Our priority is to ensure that every customer gets their new Surface Pro as soon as possible. We are replenishing our supplies as quickly as possible."