I am encountering this as well. After getting it on my main PC, I downloaded the trial to my laptop, which had not had HL installed before.
On both, I can duplicate the issue everytime. I simply create a new Pathfinder character (with yesterday's data files), add 1 level of wizard, go to the Wizard tab and click on "Add level 0 spells." or when trying to do this with the actual character, click on "Add level 1 specialized spells." did this as well.
I can't confirm it, but it appears that after this was thrown, if I click on the Spellbook, the names of the spells do not match the descriptions - almost like the index was thrown off.
If I click on Spellbook before clicking on the memorize button, it does allow me to click on the Add level 1 specialized spell button and it brings up a menu with a few spells. If I select one, it lists it on the memorized spell list, but has the following two sentences on one line:
"Excess level 0 specialized spells. Add level 1 specialized spells". At the bottom is an exception thrown that says, "Wizard: Add more specialized spells!"
Every time, the same error is thrown in the HL log files
C:\HeroLab\HeroLab.exe
3.4.a 197
ACCESS VIOLATION
Address: 0x0049a1cf
Type: bad read
My desktop pc runs XP64 SP2 and my laptop runs Windows7.