Slides not opening. .Office 2010 ..

Facing issues while opening any Powerpoint slides and also word files. It says verifying your login credentials for a long time and then says Service not available as you do not have access. This error comes only in the morning from 9 to 9:30 am. After that it works fine.
Sometimes we get this error also
"This service is temporarily unavailable. Ensure that you have connectivity to this server. This error could be caused because you are working offline, your proxy settings are preventing your connection, or you are experiencing intermittent network issues"
 
........ Experiencing this issue when trying to open powerpoint or word  from network.. Please suggest what could be the reason .. Also please suggest the solution .. Please.. Its very important and urgent.. Thanks
 
Word and powerpoint installed on win 7 system. People who are accessing this system are trainees. Trainees will have limited access. After downloading the file word/ppt to the system.. when thy try to open it .. they are facing this error. Can you please suggest me a solution for this.. Its very Important for me.. Please