This bug has been reported on Ubuntu Launchpad as:
After renaming a folder and enter it the folder itself is marked as active (colored) but by hitting 'Enter' again the folder does not open.
Enter has no effect!
In older versions of Thunar you could enter the folder at once by hitting twice 'Enter'...
Linux ubuntu 2.6.31-14-generic #48-Ubuntu SMP Fri Oct 16 14:05:01 UTC 2009 x86_64 GNU/Linux
DistroRelease: Ubuntu 10.04
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100427.1)
Package: thunar 1.0.1-3ubuntu1
PATH=(custom, no user)
ProcVersionSignature: Ubuntu 2.6.32-22.33-generic 22.214.171.124+drm33.2
Uname: Linux 2.6.32-22-generic x86_64
Looks fixed in master.