Webserver - "Failed to Connect to SBOCommon -111"

hi, i have a little web-application, that connects to the SAP-Db via DIApi.

it worked fine on the test-server, but now in the live-environment it crashes from time to time (i can't login and get the error message mentioned above).

After a restart of the IIS it works again.

What can it be? Has anyone had the same problem?

best regards

Philipp