You are looking for 3.0.30 even though the newest looks like it is 3.30?
I wasn't sure how to find the old versions, but it looks like if you go to the driver download page (http://www.digi.com/support/productdetail?pid=4680) you can replace the H1 in the URL with F and you'll get the download link for the 3.0.30 version.
64 bit zip - http://ftp1.digi.com/support/driver/40002668_F.zip
64 bit exe - http://ftp1.digi.com/support/driver/40002668_F.exe
32 bit zip - http://ftp1.digi.com/support/driver/40002670_F.zip
32 bit exe - http://ftp1.digi.com/support/driver/40002670_F.exe