Microsoft is investigating reports that about a dozen models of Skype-certified phones are having trouble logging into the IM, VoIP and video-conferencing service.

"We are sorry to hear about these difficulties and we are doing our best to look into this matter to resolve these issues," a Microsoft community representative wrote in the official Skype support forum.

The official acknowledgement listed at 12 models that could be affected by whatever is causing the issue, including phones from Panasonic, Linksys, GE and NetGear.

According to multiple discussion threads posted in the section for "Other Devices" of the Skype official support forum, the problem apparently started this weekend.

Some affected customers need the problem solved immediately, especially those who use Skype for business communications.

"Can anybody answer how we get through to Skype to fix this problem urgently. We rely on these phones for our business and have a call contract in place which we can obviously no longer use so it is affecting our business badly," wrote a user identified as "GTEDevelopments" in a thread titled "NetGear SPH200D problem."

Microsoft didn't immediately respond to a request for comment.