SMBFS/CIFS - can't navigate to paths with spaces

Using Ubuntu Server 10.04 LTS, I recently upgraded to the latest samba and smbfs via apt-get, and when I mount our windows share via SMB, I'm getting this kind of error:

root@orbital testsmb/test# mkdir "spaces test"

root@orbital testsmb/test# ll
total 5
drwxr-xr-x  3 nobody nobody    0 Aug  4 17:32 .
drwxr-xr-x 37 nobody nobody    0 Aug  4 17:24 ..
drwxr-xr-x  0 nobody nobody 4096 Aug  4 17:32 spaces test

root@orbital testsmb/test# cd spaces\ test/
dirname: extra operand `test'
Try `dirname --help' for more information.
dirname: missing operand
Try `dirname --help' for more information.
-su: [: =: unary operator expected
basename: missing operand
Try `basename --help' for more information.

root@orbital /spaces# pwd
/home/testsmb/test/spaces test
dirname: extra operand `test'
Try `dirname --help' for more information.
dirname: missing operand
Try `dirname --help' for more information.
-su: [: =: unary operator expected
basename: missing operand
Try `basename --help' for more information.

Even using quotes, single and double, don't work:

root@orbital /spaces# cd ..
root@orbital testsmb/test# cd "spaces test"
dirname: extra operand `test'
Try `dirname --help' for more information.
dirname: missing operand
Try `dirname --help' for more information.
-su: [: =: unary operator expected
basename: missing operand
Try `basename --help' for more information.

root@orbital /spaces# cd ..

root@orbital testsmb/test# cd 'spaces test'
dirname: extra operand `test'
Try `dirname --help' for more information.
dirname: missing operand
Try `dirname --help' for more information.
-su: [: =: unary operator expected
basename: missing operand
Try `basename --help' for more information.

Here is my sanitized /etc/fstab:

//192.168.xx.xx/winshare      /home/testsmb  smbfs   rw,credentials=/etc/samba/winshare.creds,uid=nobody,gid=nobody,auto   0       0

• None of this happens on local file systems.
• Also an older SuSE box with an ancient smbfs doesn't run into these problems.