Sarge+Kernel 2.6.8 -> Why not 4GB of heap memory for Java?

[Christian Hammers <ch@westend.com>]

Hello

With Debian (Sarge+2.6.9) on a machine with 4GB RAM, I cannot get SUNs
Java (1.4.2-02) to allocate >1GB of heap RAM. 

This works on a RedHat machine though. Now our customer wants
this to be fixed, if we don't want to switch to RedHat :-(
Any ideas what this might be? Missing Kernel feature, too old libc6
(malloc)? 

$ java -Xmx3500m -cp . HelloWorld Hello World
Error occurred during initialization of VM
Could not reserve enough space for object heap

bye,

-christian-