Sender Failed

Hello,

use the plugin to make submissions already for some time, but in recent weeks, is failing to send.
I have more than one list with about 500 users per list, but when I do the shipping, I see that never complete submission to all the list, always sends less than the total, the majority is always around 300.

I also noticed that when simulating the cron via javascript the screen goes blank, and can only perform to access the menu Senders.

to accompany the console browser, only once he showed me the error that it was not possible to write to the temporary folder (or something).

Already cleared the temp folder in knews plugin more the fault persists.

Use IIS 7, WordPress 3.6.1 and 1.6.2 Knews

Thank you very much.

https://wordpress.org/plugins/knews/