out of memory Errors

[Prabhat Rana]

I'm running BIND 9.6.1-P1 in a Solaris 10 server. There is a total of 32G of physical memory and at any given time about 20G is free. However, named keeps on throwing "out of memory" errors. When these error occurs in syslog, although named is still running it goes in a hung state.
I noticed that it occurs when named takes up 4G of memory. So it appears as if there is 4G of memory usage limitation in this environment. Although there is plenty of physical memory available, named is not able to go more than 4G. 
I looked around and one way as documented by some Oracle DBA was to create projects in Solaris 10 environment as in /etc/projects file and assign more memory. I followed those steps but it didn't fix the issue. 
Has any one come across this problem? Is there a way to find if the BIND is 32 or 64 bit?
The BIND pkg was downloaded from http://sunfreeware.com So we're not sure if its 32 ot 64 bit.
Any suggestions would be greatly appreciated.

Prabhat.