Rather than post in all the threads where this has been discussed, I thought I would start a new thread. I received the following from HTC Tech Support and have their permission to post it here. I have not tried this myself.
Thank you for your inquiry about the Sprint Mogul. I understand how frustrating it is that you cannot maintain a sync relationship between two computers. You have already found out how Microsoft resolved this issue within certain software builds of Windows Mobile 6.1. The software build of Windows Mobile that is required to bypass this problem is known as AKU version 1.2.6 or higher. With each new update or phone release, HTC uses the latest build of Windows Mobile from Microsoft. That is why it would require a ROM update to update your phone with the latest versions of Windows Mobile to avoid the sync error that you have received. I do not know of any plans from Sprint to order a ROM update for the Mogul, it is at their discretion to do so.
Since I cannot advise you of any software fix, I was able to find one series of steps available online that appears to have worked for some people. I have not been able to replicate the problem or test these steps, so I cannot guarantee if these will work. These steps are not verified to work, although I have added comments to explain the risks and precautions that I would use in these steps. If this does work for you, then I would like to know if this has resolved the issue you have synchronizing to both computers. You must successfully back up the information on your phone to one of the PC's before doing these steps. Please read all steps before starting, as there is a risk of losing your personal data if this is not performed correctly.
*Steps taken from others users on Internet forums
1. Backup PIM (Contacts/Calendar) in both Desktop & Laptop. The PIM data is the Outlook PST file. This file contains your personal data from Outlook. On each PC go to Start > Control Panel (Classic View) > Mail > Data Files > Open Folder > Select and Copy the Outlook.pst file. Paste a copy in a new location, like your PC Desktop. Rename the file as 'OutlookBackup.pst' This will be your backup of your personal information, so make sure that you know where this file is located, and is kept safe.
2. Delete all PIM entries (Contacts/Calendar) in both Desktop & Laptop. This means to remove all of your personal information in Outlook.
3. UNTICK Contacts/Calendar Sync Option in Pocket PC. (this will clear all PIM data in your Pocket PC). On the phone, go to Start > Programs > ActiveSync > Menu > Options > Remove the options that are checked in this screen. This will remove all of your Contacts, Appointments, Tasks, and sync Emails from your phone.
4. Sync both Desktop and Laptop, ensuring that ActiveSync is achieved between Desktop & Laptop & Pocket PC WITH NO DATA. ActiveSync a few times with Desktop & Laptop WITH NO DATA. Remember, you have deleted your personal information from Outlook and the phone, so this only establishes a sync partnership with blank information fields.
5. Import all PIM entries into Desktop. In Outlook, go to File > Import and Export > Import from another program or file > Personal Folder File (.pst) > browse to find 'OutlookBackup.pst' from the Desktop > Select Personal Folders, check "Include Subfolders" and "Import items into the same folder in: Personal Folders"
6. Sync Desktop to Pocket PC. Make sure that you selected the options to sync your personal information again. Use the PC sync software to make sure the options for Contacts and Calendar, etc, are selected for the sync.
7. Sync Pocket PC to Laptop.
8. Sync Pocket PC to Desktop.
9. Import all PIM entries into Laptop In Outlook, go to File > Import and Export > Import from another program or file > Personal Folder File (.pst) > browse to find 'OutlookBackup.pst' from the Desktop > Select Personal Folders, check "Include Subfolders" and "Import items into the same folder in: Personal Folders"
10. Sync Pocket PC to Laptop
11. Sync Pocket PC to Desktop
12. Sync Pocket PC to Laptop
If you end up with duplicate data due to the import process, then I recommend deleting the duplicates on one PC, then synchronizing the phone to automatically remove the duplicates from the phone and other PC.
I hope we have answered your question in detail. Feel free to contact us again if you have any further questions.
HTC Technical Support
http://www.america.htc.com
http://www.htcwiki.com