white screen after theme activation – again

Hi there, first post so go easy and all that.

I have seen posts about this problem already but I seem unable to solve the problem. I can use any of the default themes without an issue, but anything that is uploaded results in a white screen if activated – I am even unable to preview themes uploaded to the system. I have tried downloading the zip to my local machine and uploading from there but still no luck.

I have also tried with both firefox and IE8 with similar results and the problem is theme-independent.

In order to get the uploading to work I did have to modify the wp-config.php file as per this post:

https://trycatch.iblogger.org/web/unable-to-locate-wordpress-content-directory-wp-content

otherwise I kept getting asked for an ftp login which never worked.

Currently have wordpress 2.9.2 installed on ubuntu 10.04.2 server edition.

Any help would be great