Fatal error: Cannot redeclare class DateTime after Ubuntu upgrade

[apjjr]

I was running the community version Sugar 4.2.1a on Ubuntu 6.06 LTS. Worked great.
I upgraded to the new LTS version 8.04.

The first time I tried to login to Sugar, I got the login screen. After logging in I got the following message:

Fatal error: Cannot redeclare class DateTime in /var/www/SugarSuite-Full-4.2.1a/modules/Calendar/DateTime.php on line 29

Now I get that message every time I try to get to Sugar instead of the login screen.

If I go to http://ls2/test/phpinfo.php on my server, it displays:
System Linux LS2 2.6.24-16-386 #1 Thu Apr 10 12:50:06 UTC 2008 i686
Build Date Feb 27 2008 20:27:58
Server API Apache 2.0 Handler
Virtual Directory Support disabled
Configuration File (php.ini) Path /etc/php5/apache2
Loaded Configuration File /etc/php5/apache2/php.ini
Scan this dir for additional .ini files /etc/php5/apache2/conf.d
additional .ini files parsed /etc/php5/apache2/conf.d/curl.ini, /etc/php5/apache2/conf.d/mysql.ini, /etc/php5/apache2/conf.d/mysqli.ini, /etc/php5/apache2/conf.d/pdo.ini, /etc/php5/apache2/conf.d/pdo_mysql.ini
PHP API 20041225
PHP Extension 20060613
. . .

Anyone know what I can do to fix this? I know I should have upgraded as they were released. Should I install the latest version now?

Thanks for any help,
Alex

[apjjr]

I got the old 4.2.1 to work again by following the instructions in http://www.sugarcrm.com/forums/showthread.php?t=23319

I think now I will backup and do the upgrade to4.5.0d with the upgrade wizard then to 5.

Alex