That is strange, there was a bug in TinyMCE paste as text when using Chrome that made me previously revert to 3.2.7, if those files are still on disk you can switch back to it from config. However, version 3.3.7 actually fixed it which is why I upgraded to 3.3.7. I guess it is possible that browser updates have broken it again.
Please indicate what browser(s) you are having this issue with?
They recently released TinyMCE 3.3.8, maybe that will fix it, I will see about upgrading.
My favorite editor at the moment is CKeditor though it has a few quirks as well.