Uninstall "Logbook Pro Pocket PC Companion" from your Windows Control Panel Add/Remove programs area. This will also bring up the ActiveSync Add/Remove programs area, when you see that dialog, click "NC Software Logbook Pro" then click the Remove button.
On your Pocket PC, using File Explorer, delete these two folders:
/My Documents/Logbook Pro
/Program Files/Logbook Pro
(Of course, only delete the Logbook Pro sub-folder)
Download and install this file to your PC, make sure your Pocket PC is cradled and connected via ActiveSync:
http://www.logbookpro.com/download.aspx?ProductID=212
After this is completed and you confirmed also that Logbook Pro for Windows 1.10.26 (or later) is on your PC and you also have the Microsoft .NET Framework 1.1 installed on your PC, start then close Logbook Pro, then launch Logbook Pro on the Pocket PC.
See this link to verify you have, or download if needed, the .NET Framework 1.1 for your PC:
http://msdn.microsoft.com/netframework/downloads/framework1_1/
Note: There is also a version 2 of the .NET Framework, Logbook Pro specifically uses the .NET Framework 1.1 version, however, we suggest installing both v1.1 and v2.0 as our future products will use v2 on the PC side.