Troubleshooting
When things go wrong with OneNote, as they occasionally may, there are a few steps you can take to remedy the situation.
SafeBoot
One quick troubleshooting step you can take with OneNote is to start it with the /safeboot switch. Start | Run | Onenote /safeboot. OneNote will start and present you with a couple of troubleshooting options. One of these options is to clear the OneNote cache (see below) and the other is to clear the customized user settings, which basically resets OneNote back to the default.
Delete the Cache
OneNote uses a local cache file to improve performance, reliability and sharing. All work in OneNote is actually done to the local cache file rather than the actual data file and then those changes are quietly sync'd to the data file in the background.
Sometimes the cache in OneNote 2007 can get corrupted and the best way to troubleshoot it is to delete it. Assuming all of the changes you have made have already been committed to the data file deleting the cache will not lose any data - but if you're at the point where you're deleting the cache file you're probably fairly desperate anyhow so a little bit of data loss may be an acceptable price to pay to get the application back on its feet.
The cache file is typically found in the: C:\Users\[username]\AppData\Local\Microsoft\OneNote\12.0 folder if you're running Vista or the C:\Documents and Settings\[username]\application data\local\Microsoft\OneNote\12.0 folder for Windows XP. With OneNote closed, using Windows Explorer go to that folder, find the OneNoteOfflineCache.onecache file and either rename it, move it or delete it. I usually recommend renaming it so that if this fix doesn't work and you decide you want to you can always rename it back.
When you start OneNote it will automatically recreate the file; hopefully without whatever corruption caused the problem.
Print to OneNote on 64-Bit Operating Systems
One issue that comes up increasingly is the problem of printing to OneNote when you have a 64-bit operating system installed. For quite some time this was a problem for OneNote 2007 users who were running on Vista or Windows 7, 64-bit. But then OneNote PM David Rasumussen rode to the rescue in his blog entry here...
Note that this is not an issue with the new 64-bit version of Microsoft OneNote 2010.
Where are OneNote 2007 Files Saved?
Depends slightly upon the operating system you're running but...under your Documents (or My Documents) folder you should find a "OneNote Notebooks" folder. Your notebooks are all in there.
Why are my Notebooks suddenly all read-only?
If OneNote suddenly opens everything as "Read-Only" and many of its options are greyed out that usually means that either you haven't activated the product or you're using a Trial version of OneNote that has expired. Check the Help menu.
If you're sure you've got the full version of OneNote (not the trial) and you have activated it then the next thing to check is to make sure that you have read and write permissions to the folders and files. In Windows Explorer navigate to the folder containing your notebooks (see above), right click the folders and .ONE files and choose Properties, to make sure none are set to Read-Only.
How Come My Pens are greyed out?
One of the mysteries of the OneNote universe. Pressing Windows Key + V disables the pens toolbar in OneNote. Press it again to reenable.
For more tips and tricks on working with OneNote see http://www.officeforlawyers.com/onenote.htm