Skydrive suddenly stopped syncing with my pc.

My skydrive has suddenly stopped syncing with my pc. When I rightclick on the icon on the taskbar the sync button is not active. I have had no problems until this. I have tried on my laptops, and it is the same problem. I have loads of space available, and my account is fine. Others have succeeded in uploading into our shared folders, and syncing with their pc's and mac's. Like them, I can upload directly to those folders by dragging directly to Skydrive, but not through my pc skydrive folder.