Huh, that's a kind of odd format for the record. Try filling out our DNS form with…
Update, May 2012: Note that this post was written back in 2011; it looks as though the format has changed since then. To generalize a bit, here's how to put together a SRV record of any type for DreamHost's DNS panel. Replace all of the all-caps words, other than "SRV", with the appropriate value from the Lync control panel (or whatever else):
Name: SERVICE.PROTOCOL (the underscores are important)
Value: PRIORITY WEIGHT PORT TARGET
The "Name" and "TTL" aren't needed. (The Name is just your domain name — it's implied by the domain you're editing DNS for — and an appropriate TTL is already applied to all records.)
Here's an example. Note that your results may look a little different if Lync has changed their setup since I last updated this.
Value: 100 1 5061 sipfed.online.lync.com.