I have been using Atahualpa for over a year and ran into a problem last night that I not sure has been described in the forums so I decided to post my problem and how it was solved so that maybe others who run into it may be able to fix it.
My web server is Host Gator. I'm using version 3.4.9 on my test site and 3.4.6 on my live site. Both sites had the same problem which just started yesterday. When I try to SAVE from the style & edit CENTER COLUMN tab I get thrown into my generic error page (I'm a newbie here ... not even sure what error I was getting).
After searching some of the recent forums on the Host Gator site I found that others have been getting 403 errors that they attributed to Host Gator enabling some new mod-security-rules, something to do with monitoring data in POSTS (again .. newbie here) specifically if "http://" is found in the post.
In the CONTENT ABOVE the LOOP field of the CENTER COLUMN styling tab there is a comment in the post data that after I removed this comment I was able to save the changes to the styling again
/* For the plugin Page2Cat http://wordpress.org/extend/plugins/page2cat/ */
I think there are other ways to fix this via a .htaccess file change ... but I'm not savvy enough to understand what's required to do this. Hopefully this information is helpful to someone else.