Who I have the same questioned this topic

I am using a Samsung Intensity II phone.  From time to time I am unable to read text messages sent to me from my friends who are using smart phones.  Most of the time, it is because they have included emoticons and once they re-send the message without the emoticon, I can read it just fine.  However...

Last week, the problem became much worse!  Suddenly, I can't read messages from two of my friends (who already know not to use the emoticons).  They both tell me that they aren't doing anything different, but it is now impossible for us to communicate via text.  Any messages I receive from them look like they are written with foreign language characters (like Chinese or Japanese kanji).

Can someone help?  Any suggestions would be appreciated!