Does your folder (and the snippet, when you click on the folder) show up in the Code Snippets Manager? If not, then maybe it didn't get added correctly (or VS 2010 didn't parse the snippet successfully, or didn't recognize that the file was a valid snippet)? I believe the folder will only show up in the Code Snippets manager if VS2010 finds something it recognizes as a valid snippet, so if there are any parsing issues, there might be problems.
If the folder does show up correctly, then I also did notice that, when you hit Ctrl-K, Ctrl-X, unlike in Visual Studio 2008, newly added snippet folders appear to be sent to the bottom of the list instead of being sorted. In VS 2008, I was able to stick an underscore before the folder name (e.g. _Code Snippets) and have it show up on top. Not so, here. I realize this might be an idiotic suggestion, but maybe it's at the bottom of the list instead of sorted in with the rest? I know, I know, but I had to ask...
Barring that, maybe there is a caching issue with IntelliSense?
Not much of an answer, I know, but maybe it will jog someone's memory?