I am running K2 on Joomla v1.5.23 and want to upgrade my K2. I followed the instructions and installed the new version 2.5.1 over my existing version 2.4.1 . Once I am done and it tells me my upgrade was a success I go tot he front end of my site and refresh the screen and.... Nothing... Nothing, it's just blank. Luckily I am testing this on my test website. What can I do to fix this problem?

Try turning your joomla error reporting to highest and see if the blank page will turn into an error. This is probably a front page issue of some sort

Thanks for the pointer. The problem seems to be with the JA Newspro module. I disable them and everything works fine.

Here is the error I get for those who might have an answer:
Fatal error: Call to undefined method K2ModelItemlist::getCategoryFirstChilds() in C:\xampp\htdocs\cycle\modules\mod_janewspro\helpers\adapter\k2.php on line 40

Same problem here. My ROK Stories module became utterly useless and another content display module made the white screen of death.

I had to downgrade to 2.4.1 just to get my website working properly again!