502 proxy error

Hi all,

we got interesting problem with this template. I am not sure why, but we still get 502 proxy error (internal network) and Error 324(net::ERR_EMPTY_RESPONSE) Chrome, Page can not be load from IE or blank page from normal internet access.

Timeline:

Joomla installed, templete installed, css changed and 502 error occured. Few hours and all ok, without reason. One more css change and error back again. We found small favicon error - missing, repaired. Then few days without errors and now again 502, but no with css change only. Now with website browsing too ( example click to menu or artile update and etc.). Admin is still accessible

- Joomla! 1.5.23
- PHP 5.2.12
- My admin 4.1.22
- No template/core changes
- joomla core sef
- web structure: main web/problematic web - "main domain/abc", each has own Joomla! installation
- No special html/php/java scripts
- css and images changed only
- five more extension instaled only
- no own extension or beta/test/rc versions
- testet with new empty database, standard joomla installation and with quickstart package, all the same error
- if an error occurs and we change the template, all is ok

Server hosted 8 other joomla installations and all are ok and fully without problems.

Log has no errors

Someone got something similar or some idea where can be the problem? Some security exceptions? Too much sensitive proxy or...

Thanks a lot for any info