you can redirect stderr.
more explanation here, but having a command like:
MyCommand >log.txt 2>errors.txt
should grab the data you are looking for.
Also, as a trick, Windows bypasses that limitation if the path is prefixed with \\?\
(msdn)
Another trick if you have a root or destination that starts with a long path, perhaps SUBST
will help:
SUBST Q: "C:\Documents and Settings\MyLoginName\My Documents\MyStuffToBeCopied"
Xcopy Q:\ "d:\Where it needs to go" /s /e
SUBST Q: /D