Which client are you using when you customize the house and everything freezes/crashes? If you're using the KR client, I believe house customization is still a bit of a weak point and you may end up being far less frustrated if you use the 2d client if you will be doing a lot of building or revamping of your house.
Also, with either client, it's a good idea to slow down with clicking on any part of the tool bar if you notice that things are getting laggy and there seems to be hesitation/slowness with the cursor becoming usable again after you do things like backup, synch, change to a different category of objects to build, etc. I think all the housing information may be stored on a separate server and at times I think communication to/from that server is delayed.