Hello, so I've got some clarification of error codes for anyone experiencing problems.
Error [36] means the patch installer is finding a file it needs to patch, but the file isn't what it's looking for. Basically the file is there, but because it checks out wrong it cannot do a differential patch on it.
The standard solution is to uninstall/reinstall before attempting to patch again.
Error [15] means the patch installer is looking for a file to patch but can't find anything at all. So, it can't do a differential patch on something that isn't there.
The standard solution is, once again, to uninstall/reinstall before attempting to patch again.
Now for both of those, the solution posted in the thread that someone else linked above:
http://social.biowar.../index/532591/1 -- this may work for both of these scenarios. I can only assume if a file is missing (error [15]) it's been renamed, deleted, failed to copy off your disc for some reason, or maybe in some *rare* cases, your hard-drive's file system can "misplace" files off your hard drive... so, maybe clean your install disc real well and run a checkdisk on your hard drive. To do that: (for WinXP anyway) in Windows explorer, right click on the hard drive of choice, properties, tools tab, error check -> scan now. Make sure the automatically fix is selected, but not the scan and recovery of bad sectors unless you have the time to let it run... that takes a loooong time. Then... reinstall and repatch! Please note that these aren't guaranteed to fix the issue, just suggestions that you try
at your own risk! *cue dramatic music*

The crux of the problem: RTPatch will look for a file to patch, and if it isn't in the right place or doesn't look "just so" it won't go ahead with the process. So, sorry to say - a reinstall is about the only standard solution. It's not ideal (and yes, it's very tedious) but it should work.
...lastly, error [29] is No Disk Space. So yes, uninstalling the character creator would fix it, as that would free up about 1 gig off your drive!

I've forwarded that one along in specific to the devs in charge, as well as a general suggestion so in the future we can possibly get the installer to kick out a little more plain english and a little less numerical coding when appropriate!