When I'm on either Opera Mini or the standard internet on the phone..I can only reply on message boards and the box to type a new thread is just a bunch of letters and symbols.
Can't say for Opera Mini because i don't use it because I don't like it but are the message boards your trying to access mobile friendly? For example, if you use Crackberry on your BB brower you need to use wap.crackberry.com
Posted from my CrackBerry at wapforums.crackberry.com