Run the fix permission option in the advanced section in the custom recovery for apps that freeze or forcecloses.
Check the md5sum of download with md5sum given by the dev. In case download became corrupt. Make sure you use Wifi on all download's straight to phone.

 

In addition, I would add: click download, set down the phone and walk away. I had big problems with bad downloads at the beginning, but once I made sure I wasn't doing anything on the phone while something was downloading (checking email, texting, etc), my incidents of bad downloads decreased dramatically.

Also, I used to frequently go into recovery to clear cache & dalvik cache. Then I started using link2SD. I've don't do that anymore, as it wrecks link2SD. And doing the recreate mount scripts thing has *never ever* worked 100% for me. Just my $0.02.

Edit to add: great guide, btw!

Edit: so I had a bunch of force closes last night. I rembered this thread and decided to try the fix permissions thing. 45 minutes (!) later it finished,I rebooted,and EVERY SINGLE app on my phone popped up forceclose notices in a steady stream until I pulled the battery. Ended up having to do a full wipe & reflash. *moral of the story:1. Nandroid backup before fixing permissions,2. Don't fix permissions if u are using link2sd, 3. Don't attempt any of this right before bed,thinking its a quick process