I have the same experience on trying to put facebook like box in my blog.
Yes there is 2 different blogs relate with how its hosted :
1. WordPress original hosted (user cannot add any plugins, limited widgets)
2. WordPress - self hosted (All wordpress files placed in separate server, so user able to add or delete many plugins)
I have above 2 categories of wordpress blogs. In type number 2, it is very easy to apply the like box because there are many widget avaliable tobe downloaded and apply (upload) thru my hosting. Here it is : http://www.asyahome.co.cc
Just download facebook funbox or like box widget, then upload to plugin directory, go to dashboard, activate it, insert the profile page number, it's done.
But in the type number 1 as mentioned above, the only way to apply like box is copy the code and paste it, but I dont know why it is not worked, many articles in google said that just simply paste the code in the "text widget" of wordpress, but thousand times i tried, the more i got frustated, and not even single article I found which has the solution.
Please see my blog http://www.asyahome.wordpress.com, For a note, actually about 6months ago it already have the fanbox, but Im not quite remember how it applied and why it just dissapeared. As I remember, there was a "facebook fan box widget" in my "appereance" dashboard, i only put my "Facebook API code" then its done.
I dont know why the "facebook fan box widget" is not there anymore, but the twitter widget come up.
I do frustrated, please anybody give me a simple explanation to resolve, its for many many peolpe who in the same frustrated line also. :)
Meanwhile I keep on observating, once I got the answer, I'll be back.