Roundcube HTML format problem

HellO!

Have problem with Roundcube on my second server in roundcube error log:

Code:

[03-Dec-2010 12:36:03] PHP Warning:  include(DOMDocument.php) [<a href='function.include'>function.include</a>]: failed to open stream: No such file or directory in /home/admispconfig/ispconfig/web/roundcubemail/program/include/iniset.php on line 106
[03-Dec-2010 12:36:03] PHP Warning:  include() [<a href='function.include'>function.include</a>]: Failed opening 'DOMDocument.php' for inclusion (include_path='/home/admispconfig/ispconfig/web/roundcubemail/:/home/admispconfig/ispconfig/web/roundcubemail/program:/home/admispconfig/ispconfig/web/roundcubemail/program/lib:/home/admispconfig/ispconfig/web/roundcubemail/program/include:.:') in /home/admispconfig/ispconfig/web/roundcubemail/program/include/iniset.php on line 106
[03-Dec-2010 12:36:03] PHP Fatal error:  Class 'DOMDocument' not found in /home/admispconfig/ispconfig/web/roundcubemail/program/lib/washtml.php on line 265

I can open emails in HTML format. If i use text format all works great.

How to resolve this problem.

Big thnks.

 

Does DOMDocument.php exist? What's the output of

Code:

updatedb
locate DOMDocument.php

?

 

Output is empty.

 

OK.

But how I can to resolve this problem?
I have new server with fresh ISPConfig2 final installed and RounCube 0.4.2 installed.

Thnks.