Most of the LDAP connections from IBM WebSphere Application Server are configured with TLS. So you need to have the root certificate in the WebSphere truststore to connect.
Today I learned a new lesson during troubleshooting a IBM Connections System. I updated to 6.0 CR2, updated WebSphere to FP13, last fixpack for Docs and so on. You will ask if I added IFP88438 to the list, be sure that I installed this fix which reanables the root element in Federated Repositories. Have a look at WAS 8.5.5 FP12 breaks Domino “root” base entry setting for more details.
Then one of the two deployments showed strange behavior with Activities. On the Activitystream I only got an orange error symbol instead of the Todo list and when I opened Activities directly I got an empty page.