Back in July, Google sent out new requirements for their Google merchant feed specification. Those requirements go into place 16 days from now, on September 22nd.
Ronald from the Google Merchant Center team wrote in a Google Merchant Help thread:
As we announced in July, the new Google Product Search Feed Specification and Policies will go into effect on September 22, 2011. After this date, accounts that do not comply with the new requirements may be suspended.
Please visit the official Google Merchant blog for more information on this update.
For more on the specific changes, see this help page.
Forum discussion at Google Merchant Help.