I am unable to upload photos into my blog with ver 2.5.1. I had the same issue with 2.5 (just starting blog).
I tried using Flexible Upload and like the interface but it's not working either. I get this error message:
"File 0: The uploaded file could not be moved to /var/www/vhosts/beginningtaichi.net/httpdocs/blog/wp-content."
I'm a newbie and have minimal skills. My web guy is very knowledgeable but not with WP.
I checked the Forum and found people with this issue but didn't always understand the solutions given.
Thanks for your help.