I don't come across this issue very often, but when a client brings it up, I know exactly what the problem is by the fact that it's so completely not obvious. Just yesterday, I had a client call up complaining that part of their massively long article was being cut off after form submission. No errors were thrown and the page processed normally, just with less data.
I encountered this for the first time maybe two years ago. It was such a pain in the butt to figure out. The problem was the Long Text Buffer Size in the ColdFusion administrator for the client Data Source. This is set as the number of characters that can be passed through ColdFusion in one textarea variable. That is the problem, but the REAL problem is that when you exceed this character limit, the server does not tell you that this is happening; it merely gives less data.
I had that exact same pain in the butt about 6 months ago when building a small app to store documents within a database. After I'd convert the whole thing to binary and base64 encode it. it would store just fine. But upon retrieving and trying to reassimilate it, SOME of the time it would fail...turned out only on the larger files that, when encoded, exceeded that admin limit. Anywho, I feel ya. It's good that you put this little tidbit out there.
Hello - I had this exact error and have never forgotten it - the previous writer of an app was saving cfcontent af all the form HTML - when it went over the limit it displayed only half his expected data.... - a great way to learn ... The fix was turning on the CLOB & BLOB in the Database mappings ... for me anyway ... [ I hope that is what we are talking about ]