You are getting that error because ISPConfig 2.2.19 updated ClamAV to 0.92 and PHP to 5.2.5. They will not compile on the version of gcc you have (4.0.2).
Unfortunately, gcc 4.0.2 is the latest in the FC4 repository. The best solution is to update to FC7, FC8 or CentOS. Then you will have gcc 4.1.2.