Same here too. Attempting to open any Office file from the home share using MS Office 2008 for Mac results in an error. Either stating that the file is read-only or corrupted. However, if the same file is copied to a local drive or another non-home share - the file opens without issue.
I'm not convinced that this is necessarily an issue with the drive mapping as Mac OS volumes are mounted as /Volumes/ShareName
so home would be /Volumes/home but there's definatley some issue there.
Interestingly, OpenOffice (tested with v3.3) doesn't seem to exhibit this problem.
My Macs running lion & to be honest I'm not sure whether this issue was introduced by the Lion upgrade or DSM 3.2 beta