Apologies for this annoying issue. I could type a lot about this. I will save you the headache. There is more info in other threads.
Ive been trying for an unbelievable 3 hours to respond to your post. This particular failure is not due to technical reasons.
I'm best just trying to leave it with Erics explanation that its a collation problem with the extended ASCII charset. Standard inverted commas (U+0022) should be fine. The pound and euro are the most common culprits . I have also been caught out with the copyright c.
If you do get an error, make sure you move away from the errored post. Dont try typing again a message in the same "post reply" screen . eg dont use the back key, then delete the text and typing a new message in the same window. session cookies remember it and throw the same error.
Once again sorry about this, I am aware but just tight now I do not have the required resources to fix it.