Disclaimer: I'm new to LMCE and still trying to find my way around the web admin, and writing this from memory... If someone wants to clean it up, fill in the gaps, and make a wiki entry I think it would help a lot of people out.
Special Note: First and foremost, the plug and play functionality of USB UIRT is NOT an lircd setup. This may be spelled out somewhere, but it was lost on me. Once I figured that out with confirmation from tschak909 I quite trying to fit steamzap into a lircd configuration and started making progress. It's also worth noting that it is is likely possible to setup USB UIRT as an lircd device, but I didn't go that way and it's likely counter productive unless you have a complicated remote and an existing working lircd configuration file for it.
Step 1: Verify USB UIRT is installed and configured. Once you plug in the USB UIRT it should be plug and play and add both the USB UIRT device as well as the Windows XP MCE Remote (USBUIRT). Go to Wizard->devices->media directors. Near the bottom of the page you should see the MCE remote listed, with the Infrared Receivers pulldown set to USB UIRT 0038.
Step 2: Add your remote. From the Media Director Wizard, simply click the Add Remote button and go through the add/create steps. If you are doing a streamzap (apparently the model number for the remote is PC_Remote), you will likely have to start with Add Manufacturer to put in streamzap, then close and re-open the window to be able to select it. The Device Category should be changed to USB-UIRT remote controls, but I took the long way to figuring this out, started with Remote Controls < Peripherals, and fixed it in the next step.
See the image below for steps 3 through 5
Step 3: Configure the remote correctly. Go to Advanced->Configuration->Device Template, find the remote you just added, and click the Pick Template button. This brings up the Edit Device Template window. If not already set, change the Device Category to Peripherals - Remote Controls - USB-UIRT Remote Controls.
Step 4: Add the Configuration (string). In the Device Data box, add the new parameter Configuration (String). Put the key codes in the Default Value field. For the configuration I grabbed the config for the MCE remote (USB UIRT) for the button names. Then I did a tail -f on /var/log/pluto/53_USB_UIRT_0038.log and as I pressed each button on the remote I grabbed the codes from the error message and built a configuration from that. BTW, I did this in OO Word Processor, not the web page. The box is way to small. I had to do this twice to get both key codes for each key. Perhaps someone else can explain this better, but it appears remotes send two different key codes depending on if you hit the button once or twice. The configuration codes I am using are listed at the bottom of this post. I also clicked the Use Master Device List Defaults box because that's the way the Windows MCE remote was setup, and again I don't know what it does.
Step 5: Add the Remote Layout (String). In the Device Data box, add the new parameter Remote Layout (String). For the Remote Layout (String) entry I just used the same setup as the MCE Remote. I have no idea what the default layout of "W" is, but without a Remote Layout (String) entry, the router will not reload. It loops on an error (apparently 50 tries, but I didn't let it go that far). Hopefully someone can better explain what this does and what options other than W are for.
save and close the Edit Device Template window
Step 6: Remove and re-add the remote. Back to the Media Director Wizard. Remove the remote, add the remote, then update the MD. After this you should be prompted to reload the router, if not do a quick reload.
At this point you should have a working streamzap (or other) remote.
I will try to keep this post updated if/when anyone finds corrections to this process.
streamzap remote config:
power 1500003C96C2 1300000C5BF6
stop 150000365FF6 170000F697C2
record 170000E597C2 150000255FF6
pause 150000345FF6 170000F497C2
play 1700009897C2 150000385CF6
rewind 150000275FF6 170000E797C2
fastforward 170000E197C2 150000215FF6
skipback 1300000E5FF6 1500003E97C2
skipfwd 170000FE97C2 1500003E5FF6
back 1500002797C2 1300000F5CF6
up 150000305DF6 170000B097C2
left 170000B297C2 150000325DF6
ok 1300000F5DF6 1500002F97C2
right 170000BA97C2 1500003A5DF6
down 1300000B5CF6 1500002397C2
volup 170000EF96C2 1500002F5BF6
voldn 170000A05BF6 190002D096C2
chup 170000ED96C2 1500002D5BF6
chdown 150000295BF6 170000E996C2
mute 170000F696C2 150000365BF6
menu 130000095CF6 1500002197C2
1 1900028196C2 170000825AF6
2 150000235AF6 170000C396C2
3 1900028596C2 1700008A5AF6
4 1500002F5AF6 170000CF96C2
5 170000CD96C2 1500002D5AF6
6 1500002B5AF6 170000CB96C2
7 1900029496C2 170000A85AF6
8 1500003C5BF6 170000FC96C2
9 170000FE96C2 1500003E5BF6
0 170000805AF6 1900028096C2
red 190002A094C2 170000C052F6
green 170000C252F6 190002A194C2
yellow 170000D394C2 1500003352F6
blue 170000CA52F6 190002A594C2
screenshot showing steps 3 through 5: