php issue accessing Opportunities in SugarCrm

[wprauchholz]

I run SugarCRM under Centos4.3 with the following versions:
mysql-4.1.20-1.RHEL4.1
php-4.3.9-3.15
httpd-2.0.52-22.ent.centos4
kernel-2.6.9-34.0.2.EL
SugarCrm: patch 4.2.1

When trying to access an poortunity, instead of taking to the maintenance scrren of it, a pop-up windows appears as shown in the attached file.
I can access other modules (e.g. Accounts, Contacts, etc...) with no proble,
Anybody knows what is wrong with my parameter settings?

Thanks for your help.

[wprauchholz]

Is there nobody who has had the same problem and can throw me a lifeline?