Trying to launch javaws application manager or jnlp app by javaws command, it hangs while launching on Red Hat EL 4. No problem on Red Hat EL 3.
Following is the stack trace of javawsbin process.
[root@tequila ~]# pstack 19649
#0  0x001d47a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
#1  0x00276752 in do_waitid () from /lib/tls/libc.so.6
#2  0x0804ffe6 in sysExec2Buf ()
#3  0x0804b3aa in UpdateJREInfo ()
#4  0x0804b920 in RescanJREs ()
#5  0x08049b8b in main ()

Tested with 1.4.2_09 FCS and 1.4.2_10 b01.
Following is the 2 platforms problems reproduced.

[root@tequila ~]# uname -a
Linux tequila.japan.sun.com 2.6.9-5.ELsmp #1 SMP Wed Jan 5 19:30:39 EST 2005 i686 i686 i386 GNU/Linux
[root@tequila ~]# more /etc/*release
::::::::::::::
/etc/lsb-release
::::::::::::::
LSB_VERSION="1.3"
::::::::::::::
/etc/redhat-release
::::::::::::::
Red Hat Enterprise Linux AS release 4 (Nahant)

[root@bols ~]# uname -a
Linux bols.JTC.Japan.Sun.COM 2.6.9-11.ELsmp #1 SMP Fri May 20 18:25:30 EDT 2005 x86_64 x86_64 x86_64 GNU/Linux
[root@bols ~]# more /etc/*release
::::::::::::::
/etc/lsb-release
::::::::::::::
LSB_VERSION="1.3"
::::::::::::::
/etc/redhat-release
::::::::::::::
Red Hat Enterprise Linux AS release 4 (Nahant Update 1)