Login OpManager problem

I am having serius problems to login in OpManager. I am receiving errors such:

SQLException while preparing the statement with id : 19 Cause : Invalid state, the Connection object is closed. SQL Query : select * from UserPasswordTable

none of the usernames/passwords works, not even the admin password.

So, we forced shutdown OpManager services by shutdown the server. After that we restored the database and we could access with all usernames/passwords. The version build number in use at that moment was 8050. After recover the access I have executed version upgrade to 8723. The problem once again hapened 2 days later.

OpManager information:

Build Number: 8723 (actual)

Database: MSSQL Server

How can I resolve this problem? Anyone else had the same problem?

Thanks in advance

Best Regards

Raquel