We cannot reproduce the problem here. Does the error come up for all or only some messages?
If WriteIntoCell fails only with some messages, you may wish to send an email to firstname.lastname@example.org . If this suits you, I suggest you attach to your email some sample messages that fail. Please note that Advansys treats client test data as strictly confidential.
Have you tried to use the .Text property instead of .Value?
Have you tried using my other suggestion, to replace carriage return/linefeed pairs by a space character? You could experiment with replacing vbCr and vbLf instead of vbCrLf.
I hope this helps you.