Admin interface became unavailable

Hi, suddenly in the middle of working day Admin interface has become unavailable for all users with Admin permissions on all dev machines in all browsers. The site we are developing is available. But all Kentico apps can't be launched. What can it be, and how to resolve this issue? Event Viewer does not help too much. DB query select top 1000 * from cms_eventlog order by eventtime desc brings some errors and warnings, but to fix them we need to open Pages, Page Type Page Templates and other apps. Can it be a license issue (one of the warning in Kentico cms_eventlog table is LICENSELIMITATION on ContactManagement, while this warning was also in previous days). Thanks, Evgeny