I'm having the same problem. A few suggestions were to look for Helvetica Nueue in your font book or in library/fonts and then install. I do not have that font anywhere, so I couldnt do that. I also tried deleted the com.apple.ATS folder cache in Library/caches. That didnt work. I read that if you install the iwork trial that came with ilife it may fix the problem, that didnt work.
I'm thinking maybe its something on my computer thats the problem (too old?) i have a ibook g4. I wasnt able to install iMovie b/c i didnt meet the min requirements and iphoto isnt really working that great. I'm not able to edit the text, however if you click on the event and the "i" (information) on the bottom left you can edit the name. Fine, but the dates below the event name look odd. only the beginning of it (the end date looks ok) the start dates look like it has 2 types of text on top of each or weird font. (sorry, i dont know how to describe)
I also tried Pacifict which will search your system install disks for the font, didnt work either.
Is there a place i could get this font and download it?
Any suggestions? I'm willing to try. THANKS!