Ok... I installed k2 some 2 or 3 months ago... it worked perfectly, except for the fat that my users had to make some 4 or 5 clicks to see the attachments. Today I was trying to fix this situation and found out about K2 version upgrading. I installed it and -BAM- my site is BLANK... no error message, no visual changes, no nothing it just a white screen... HEEEEEEEEELLLLLLPPPPP!!!!!!

iemschool.com/

I see a code 500 error, which usually means PHP error, but it's difficult to find where it is just by the error screen...

You can try to use this tool community.getk2.org/profiles/blogs/k2-import-export to export K2 content, reinstall K2 (the old version if you want stay on the safe side), and import.

Make a full backup prior to do anything, though.