Photoshop is not the problem. It only uses devices you have installed, it does not define them.
The only driver I saw out there says it works with 10.4-10.6:http://www.mustek.com.tw/apprg/showdriverinfo?LID=2&PRODUCTID=SE_A3USB600Pro&LSID=34
These are January 2010 drivers so they are newer. Let us know if they work out for you.