Hi Shane,
I had the exact same problem with version 2.2 RC3.
I dug around a little and found that the settings for the uplink are stored in file "settings" at /var/efw/uplinks/main/ on my box. I found that I could manually edit the file in something nice like WinSCP and get the /32 CIDR or 255.255.255.255 subnet to work.
Here is my file for an example.
DEFAULT_GATEWAY=192.168.0.10
DNS2=172.22.6.250
DNS1=172.22.6.251
ENABLED=on
MTU=
AUTOSTART=on
BACKUPPROFILE=
RED_DEV=eth2
RED_ADDRESS=192.168.0.82
MANAGED=on
ONBOOT=on
MAC=
CHECKHOSTS=
RED_NETADDRESS=192.168.0.82
RED_NETMASK=255.255.255.255
RED_TYPE=STATIC
RED_BROADCAST=192.168.0.82
RED_IPS=192.168.0.82/32,192.168.0.83/32,192.168.0.84/32,192.168.0.85/32,192.168.0.86/32,192.168.0.90/32,192.168.0.91/32,192.168.0.92/32,192.168.0.93/32,192.168.0.94/32,192.168.0.114/32,192.168.0.115/32,192.168.0.116/32,192.168.0.117/32,192.168.0.118/32
RED_CIDR=32
After you save the file and then go back in to the network setup wizard or uplink setup wizard, you'll see it's setup correctly. Now, the problem is that Endian firewall still thinks it's setup wrong, so you can't make any changes or resave in the GUI wizard. To make any changes, you'll have to do it manually to the settings file.
Now, the interesting part. I took a closer look at how my old Linux firewall setup the network card alias settings and I found that it setup all the alias IPs with a /24 even though they were supposed to be /32. My old setup has been working fine for a few years. So, I tried setting up all the alias red IPs with a /24 in the GUI wizard and it works!!
Here is an example from my settings file that is currently working fine.
AUTOSTART=on
BACKUPPROFILE=
CHECKHOSTS=80.190.199.138,64.233.183.99,pool.ntp.org,www.google.com,www.yahoo.com,www.sf.net
DEFAULT_GATEWAY=192.168.0.10
DNS2=172.22.6.250
DNS1=172.22.6.251
ENABLED=on
MAC=
MTU=
ONBOOT=on
RED_ADDRESS=192.168.0.1
RED_BROADCAST=192.168.0.255
RED_CIDR=24
RED_DEV=eth2
RED_IPS=192.168.0.1/24,192.168.0.82/24,192.168.0.83/24,192.168.0.84/24,192.168.0.85/24,192.168.0.86/24,192.168.0.90/24,192.168.0.91/24,192.168.0.92/24,192.168.0.93/24,192.168.0.94/24,192.168.0.114/24,192.168.0.115/24,192.168.0.116/24,192.168.0.117/24,192.168.0.118/24
RED_NETADDRESS=192.168.0.0
RED_NETMASK=255.255.255.0
RED_TYPE=STATIC
You'll see I set 192.168.0.1 as my first RED IP because it made things more organized to me.
I hope these examples might help someone... Good luck!
Marc