There is a lot of guessing and assumption in these posts but the bottom line is I've experienced this.
Let me explain what has happened to me with my Blackberry.
1st issue - I used to set my Blackberry right next to my docked Dell laptop. I've noticed that when my Blackberry causes my speakers to make noise my computer screen would freeze. No mouse or anything. Had to hard reboot as there was no response.
Even though I doubted it, after a few more times of this I started to suspect the BB. So, I moved the Blackberry away immediately the next time this happened. Laptop froze, then recovered after a couple of seconds. I thought it was coincidental but I have proven this over and over again. I now keep my BB away from the laptop. I cannot explain what it is affecting but it was not coincidental. I can recreate the problem.
2nd issue - I used to run with my 60gig iPod (previous to touch screen) on my hip with a belt clip. This one has a hard drive (not flash). I started having to carry my Blackberry with me since I was on-call for work. I noticed that when my BB started doing its thing the volume on my iPod would go erratically higher and lower and settle somewhere along the volume scale. Sometimes it would cause the iPod to be really loud and sometimes it would quiet it. Moved the BB to my other hip and it stopped. Moved it back and it happens. Totally re-creatable but again, I can't explain what it is affecting in the iPod to make the volume go haywire. I can tell you it is annoying to be running and have the volume crank up on you.
The point is that phones these days are doing something with their strong signals and it makes you wonder truly how much interference they really cause to other electronics. It also has made me wonder very real the cancer threat is.