Question I receive "rename failed" after loging

Hello,
I have a problem with de login.
I have a version 1.5.22 of Joomla installed in a hosting. It's working fine.
Then I wanted to install kunena 1.6.2. The installation was interrupted and I got the blank page error.

I have tried to upload to the server the decompressed files and try the installation from the folder where I have the files and it gives the same error.
Finally I have decided to copy the folders com_kunena of administrator and components to the server and to export my local database to the server. And everything seems to work well.

As administrator I can do login, i can post, the public and private side works well

The problems begin when I create a new user(the second user in the forum) .After activating when the user does login receivs the error " rename failed ". And from this moment, everything related to users gives the same mistake " rename failed ", when I want to see the list of users, the on-line users, when I go to the module of users' management, always " rename failed ".By example,

And after giving the first error " rename failed ", the public part that untill now was working well,the links of list of users or users on line give the mistake.

I have the 775 and 644 permissions.

Anyone can help me ?

Thank you

Resolved