I am at a complete loss. I've been tracking the problem on the TDOMF support forums here and I have a test bed of Wordpress 2.6.2 with the latest dev version of TDO-Mini-Forms (which I'm refusing to release until I know this issue is resolved) plus the plugins: smiliar-posts, random-posts, recent-comment, ACE, Headspace2, Contact Form 7 and Wassup. No issues. No 500 errors.
I really need more information. I need information about how your webserver is configured, how tdo-mini-forms is configured, the actual errors reported in your host's error-logs (any 500 error should have an entry in your hosts error-logs!!!), etc.
I did hit one 500 error that completely locked me out of my webpage, which is different to the errors you've reported. I checked my hosts error-logs, normally a pretty easy thing to do, and it said that there was an error in my .htaccess.
This file is used by most webservers to control the URLs and Wordpress modifies it to allow it to generate fancy permalinks. For some reason, adding ACE, Headspace2, Contact Form 7, Wassup and TDO-Mini-Forms, screws up the .htaccess. The weird thing is that TDO-Mini-Forms does not modify .htaccess nor do any kind of messing with the permalink structure, unless there is some weird cross-filter thing going on...
To resolve this problem is pretty easy. On most host configurations, you can just delete the .htaccess. Then you should be able to access your Wordpress blog (I also renamed all the plugins to fix it). Then I went into the Wordpress admin UI and in the permalink section restored the default configuration and saved. Then reapplied my original custom peramlink settings and it regenerated the .htaccess correctly. Now everything seems to be working hunky dory.
Seriously, check your .htaccess and your host's error-log if you're hitting this 500 error.
Another note- widget functionality ceased in WP 2.6.2/TDO 12 the instant you touched the form hacker. Certainly that was not intended? Widgets seem to work fine (be reconfigurable) in WP 2.6.2/TDO 11.1
You mis-understand how the form hacker works. The form hacker is not dynamically generated so if you apply changes to the form hacker you freeze the form's code. So if you later do changes to the widgets and other options, the form's code will still be frozen to the form hacker changes.
tinymyce advanced
wp-postratings
wp-supercache
wp-wall
yet-another-related-posts-pluging
plugin-central
search-everything
share-this
I'll try this plugins next, when I get a chance.