Hi All,
After failing to import LR semester 2, as reported here
http://forum.brillkids.com/little-reader-bug-reports/%27index-or-primary-key-cannot-contain-a-null-value%27/ I did following to install it successfully.
1. Export your existing playlists and categories in bulk.
a. Go to Import/Export in LR and select "Playlists" in the export section.
b. By default first entry is selected. Then hold the shift key down and scroll down to select the last entry in the list with the mouse. This will select all the entries. Then hit the "Export" button.This will ask you to enter a screen name. Enter any value you like.
c. Then it will export all your playlists in one file named Playlist1.pl (You make select a different file name).
d. Repeat the same for categories, which will generate "Category1.cat" file.
2. Copy(or move) these files (Category1.cat, Playlist1.pl) to a safe place from the Import/Export folder. On my machine Import/Export folder was C:\Users\<your-user-name>\Documents\BrillKids\Little Reader\Import-Export. I have Windows Vista. This could be different for other systems.
3. Uninstall (remove) LR from your computer.
4. Install the new version of LR.
5. Import LR semester 1.
6. Import LR semester 2.
7. Import your Category1.cat and Playlist1.pl files.
Hope this helps.
PS: Import/Export your Categories and Playlists may take time.