Could you please provides us an error log.
Unfortunatelly, from this description we are not able to address the root of the problem. That's why we need complete error log.
Error logs can be found at the "/Monox/ApplicationData/Logs" folder.
Please take into account that we need error log file in which described error occured, also it would be really helpful if you provide us (along with a log) an exact time when that error occured.