I've been having this issue with my Droid 2 for a while now. At random times, texts I send to contacts will either arrive blank or jumbled - with either random characters breaking up the letters or upside down question marks. This has happened with Blackberry, iPhone and other smartphone users.
When I went to the Verizon store, the employees said they never heard of it happening. The best solution they could suggest was turning off my phone and removing the battery once a week. I tried this, but the problem still occurs shortly after doing this.
I also read some posts that it can occur with long (more than 160 character) texts are sent, so I tried sending shorter texts. My one contact (the one with a smartphone) still received blank texts.
I'm posting this because although I've seen other complains about this (glad I'm not alone!) I have yet to find a real solution. Any ideas? Thanks for reading my ramble.