After successful rename have message: folder "." is not available

Judging from both your issues you have imce setup in a configuration different to my testing environment. The issue you have is related to an issue I was having with refreshing the directory list after a rename. In the mean time you can comment out the line that reads "imce.navigate('.');" imce_rename.js file which will stop your error. You can also use version 6.x.1.6 http://drupal.org/node/970404 which does not have the folder rename feature.

Wouldn't this work?
imce.navigate(imce.conf.dir);

I'm running into this same issue on the D7 version as well.

It appears that imce.navigate('.') is incorrect. This call attempts to navigate to the root of the directory tree, which is not allowed by IMCE (e.g. you cannot click on the "<root>" item in the tree).

I've attached a patch that fixes this issue by refreshing the current directory after a rename occurs. When a directory is renamed, the tree is updated appropriately as well.

Oops! I was working off of the wrong branch. Here's the patch for the 7.x-1.x branch.

Patch committed thanks