I just thought I would share my experience in hopes it may save someone else a headache. I have an iPhone 4 jailbroken on 4.0.1. I have a licensed copy of Intelliscreen along with a bunch of other apps I have been using for a while but the other day when I went to open an attachment my mail app started to crash. I tried everything I could think of before I just gave in and did a fresh restore, installed all my apps, same deal. So I restored again only this time I tested after each app and sure enough, once I installed Intelliscreen it started and once I removed it everything worked correctly. I have emailed their support department but I haven't heard anything back as of yet (its been less than 12 hours so that's not a big deal). Anyway, I'll post more when I hear back form them. Hope this helps someone else.