SFDC Communication error

Hi,

we are facing the following error intermittently while connecting to SalesForce.com.

' Salesforce.com: Connection timed out: connect>' and

'<Cannot start session.

com.acta.adapter.salesforce.exceptions.UnexpectedErrorException: There was an unexpected error. Salesforce.com message is Too many requests waiting for connections...>'

the job runs fine when we re-run it after some time.

Kindly help if anyone knows what actually is causing this error and how could we solve this issue.

Thanks