A solution that worked for me
I don't know how many times over the years I have spent hours pondering why various things have stopped syncing. Today I could not get Notes to sync between my computer and MobileMe. It was working fine between MobileMe and our iPhones and iPad.
I am using Mac OS 10.7 Lion but I believe what I am about to say applies equally well to Snow Leopard and Leopard and maybe Tiger. There are 2 basic ways of syncing Notes from a computer to an iPhone or orther device. Method 1 is to check the box in iTunes (first plug in an iPhone, then click on your iPhone under Devices in the left-hand panel of iTunes, the click on the Info tab at the top, and finally check the box for Notes under Advanced at the bottom). Thenceforth your iPhones are supposed to sync Notes every time you sync via iTunes. This is NOT the method I was using.
For me it is better to sync Notes on the computer to MobileMe and then work the settings on the iPhone and other devices to sync with MobileMe. To sync Notes from my Apple computer to MobileMe I had used both the MobileMe System Preference and the Mail,Contacts & Calendar System Preference. In the former I clicked on the Sync tab and then put a checkmark by Notes. I set the drop-down menu to "Automatically". For the latter system preference, I clicked on my MobileMe account in the left-hand pane, and then I put a checkmark by Mail & Notes in the right hand pane.
I don't know if both system preference activations are necessary, but once upon a time this worked for me. It was not working today and, I noticed, not for several months. I tried everything I could think of including unchecking and rechecking checkboxes, clicking Sync Now in the MobileMe System Preference, clicking Sync Now from the MobileMe menubar icon. I even activated Method 1. Nothing worked.
What finally got things going again was the following simple step. I kept all the settings as described above. I then opened the Mail application. For me Notes was set up to show under REMINDERS. (I believe there is a setting somewhere to instead have Notes show up in the Inbox.) I clicked the disclosure triangle by Notes and sure enough I had 2 Note folders: (1) On My Mac and (2)
myname@MobileMe.com. I selected (2). Then, at the bottom of the left-hand pane is a tiny gear icon. I clicked it and from the pop-up menu I selected Synchronize
myname@MobileMe.com. Immediately Notes synced!!! I was notified of 75 or so conflicts, which were due to months of making some changes on my computer, some in MobileMe, and some of one of the iPhones or the iPad. I took 10 minutes to decide one-by-one which was the most current, also looking for cases where I might have made changes in 2 or more places and then hand-writing the extra stuff. Then I clicked Sync and everything worked immediately on my computer, within seconds for MobileMe, and within minutes for the iPhones. After that, I made some more changes on the Notes on my computer and they continued to show up everywhere else.
Sorry this is so long. I hope it helps others.