You cannot sign in to your Google account through Picasa in Windows 8.1 Preview. Therefore, you cannot perform actions that require that you sign in, such as sharing photos through Gmail.
Note This issue might also occur when you use other applications to sign in to a Google account.
This issue occurs because the application cannot retrieve certain cookies located on the computer.
To resolve this issue, install update 2864806 through Windows Update.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.