Lync 2010 and F5 Load Balancer Issues with Conversation with more than 2 users

Hi I have an Lync 2010 Enterprise Pool with 2 Front End Servers. The pool fqdn has a DNS record that points to a Virtual IP on our Load Balancers.

when using Lync Client, user can chat 1 to 1 with no issues but when trying to have an IM conversation with more than 2 people I get the errors:

When contacting your support team, reference error ID 3098 (source ID 243).

Any help would be greatly appreciated. Just so you know we are using a properCertificate for the pool not a self signed.
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Jakob DigranesSenior ConsultantCommented:
Are the users trying to do web conference on LAN or external?
When doing one-to-one IM it is P2P, when multiple users connect, they use WebConferencing part (
is that url pointing to VIP?
ECS-ITUKAuthor Commented:
Thanks for the reply. Yes that URL is pointing to my VIP. All users are on the internal LAN.

Just an FYI if I add host file entry for the pool name on the 2 front end servers to point to themselves it works.
ECS-ITUKAuthor Commented:
Also getting these errors in the event logs when I remove the hostfile entry.

This process was not able to update its health status

The IM Conferencing Server failed to send health notifications to the MCU factory at
Failure occurrences: 4, since 15/10/2013 08:52:57.
Cause: Either the Front End service is not running, or poor network connectivity.
Verify that the Front End Service is available, and its machine is visible over the network.

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ECS-ITUKAuthor Commented:
No Answer
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