On Thursday there were some reports in the Microsoft Advertising Forum that advertisers were complaining they were not able to manage their accounts.
In short, they were banned from using Microsoft's adCenter product, which places search ads on Bing and Yahoo Search.
The reason they were banned was because their ads and sites were mistakenly labeled as serving up malware.
Ralph David, adCenter Community Team, said this was a mistake and they are working on fixing it. He did not specify how many accounts were effected, but he said:
We have identified an intermittent system error which has caused some accounts to be incorrectly flagged as 'Malware' and have been temporarily suspended. This issue has been escalated to our Technical Engineering Team with the highest priority in an effort to get your account up and running again as quickly as possible.
Please be aware that the Technical Engineering Team are in the US, so we may not have a resolution today. We do have support staff in the office on Saturday, so should anything come in from the Technical Engineering Team overnight, they will let you know in the morning.
As of now, I am not sure if it is fixed or not.
Forum discussion at Microsoft Advertising Forum.