I installed wordpress 3.4.1 on a shared environment (Planethoster) few days ago. I installed few plugins including last version of akismet.
but since then, I couldn't receive anymore mails. I opened a ticket to the Planethoster support and they found the problem : the spam mail folder (/home/xxxxxxx/mail/.Spam) changed from 750 to 751. And on their servers, it blocks the incoming mails (don't ask me why...). They restored the 750 permissions and the incoming mails worked correctly again.
I don't know if the problem could be provoked by this plugin. So, just in case, I would like to know if it changes the permissions of the folder of home/xxxxxxx/mail/.Spam ?