What version of SNAP did you install? It does sound like you installed the new SNAP 5.0 beta.
Did you get it from here: http://lime-technology.com/forum/index.php?topic=5904.msg162583#msg162583
NOTE: The new version is now available here: http://lime-technology.com/forum/index.php?topic=18046.msg162098#msg162098
The SNAP web ui works in Chrome and Firefox for sure because I use both constantly. There isn't really a disk dropdown menu so I'm not certain what your referring to. I've attached some quick snapshots of what will be the next available build. It's pretty close to what you should see. I have one non-unraid drive on this test server and it's precleared but not formatted.
In the pictures, I added a share name to that drive. But, since it's not formatted yet, the status still shows it as
M:no, S:no, B:no, P:Precleared
or
Mounted: no
Shared: no
Busy: no
Precleared: yes
If you drive is actually formatted and it has a share name then you would be able to right click on the row (with your drive) and choose Mount and Share. It then would be mounted and shared and the status will change to show that.
A drive that is precleared is not yet formatted. If your drive status isn't showing the P: flag then it might be formatted.
Also, if the drive is part of the unraid array it won't be touched by SNAP in any way. What is in the Managed By column for that drive?