Over the past couple months I have set up 4 new servers based on CentOS 5.4 x86 and Lasso Professional 8.5.6. I used the stock version of Apache 2.2 from the CentOS yum repositories, and the Lasso Connector for Apache 2.2 supplied with Lasso 8.5.6.
While this configuration has worked fine in testing, all 4 servers exhibited performance problems once production load was placed on the machines. httpd threads would sporadically hang and consume 100% CPU. This would usually happen within an hour of starting Apache, and lead to performance degradation, eventually to the point where the server was unusably slow.
After extensive testing the problem appears to be caused by a bug in the Lasso Connector for Apache 2.2 on CentOS. Downgrading to Apache 2.0 and using the connector for this version has solved the problem and resulted in huge speed improvements for each server I have done this on so far.