I have a few ideas you can try.
1. If your PC reports device not recognized, try another USB port (If you use a USB hub, remove that hub.
2. The "Failed to disable RNDIS to use Serial" message comes when the port is used. Try looking into Bluetooth settings-->COM Ports. If there are any ports in that setting, remove them then try again.
3.Check if you have Activesync 4.5 (The latest version as of now) installed. If not,
Download details: ActiveSync 4.5
4. Follow these directions carefully-- You have to go into a hard reset prompt but DO NOT HARD RESET. Start by pressing the power button+reset button (the hole in the back). You will receive a prompt if you want to hard reset. PRESS THE MAIL HARD BUTTON (The one that looks like a snail mail, or the 3rd button from the left) to cancel. Try to sync again
As of the software dictionary. If it is a .cab or .exe. Just try to use Bluetooth sync and transfer it to to your PDA. Then install. If it is a dictionary package for an already install program (Your description is unclear), just follow the directions given by the website of the program.