I am currently in the process of migrating our software solution from Delphi 7 to 2010. Mostly the changes have been simple and there are only a small amount of hurdles left
When PlainText is False, LoadFromStream() first attempts to load the RTF code, and if that fails then LoadFromStream() attempts to load the stream again as plain text. That has always been the case in all Delphi versions. With the introduction of Unicode, I suppose something could have broken in LoadFromStream()'s EM_STREAMIN callback handler. I suggest you step into LoadFromStream()'s actual source code with the debugger and see what is really happening.