Does Photoshop CS5.1 support TWAIN plug-in on Mac OS X V 10.7.4

Question

I am running Photoshop CS5.1 Extended V 12.1 in 32 bit mode on a Mac OS X 10.7.4 and followed instructions to install the TWAIN plug-in as written here:
http://www.adobe.com/support/downloads/detail.jsp?ftpID=4904
I restarted Photoshop, but the TWAIN plug-in does not appear in file/import dropdown as it did in my earlier version of Photoshop (see attached screenshot).
I found this discussion in the forums which implies that the TWAIN plugin is supported in CS5.5 and Mac OS 10.7 (Lion):
http://forums.adobe.com/message/3816883
Is the TWAIN plugin supported in CS5.1 and Mac OS 10.7?  If so, can anyone help me troubleshoot why the plug-in does not appear in my file/import dropdown list?
Thanks in advance.
P.S.  I prefer to use the TWAIN plug-in because I am very familiar with the TWAIN driver and how to manipulate scanner settings to get a scanned image that represents my original artwork.  I am testing the recommended VueScan and it offers more than the epson scanner driver on the mac, but I can get more work done in less time with a TWAIN plug-in because there's no learning curve.

Answer 1

Additional information:
installed trial version of VueScan, which included a Photoshop plug-in for my epson scanner.  That plug-in IS recognized (and functional) within Photoshop CS5.1.