[BusyBox] executing from tmpfs

[Brendan J Simon]

I'm using busybox.0.60.2.  I have a tmpfs mount on /tmp (using mount -t 
tmpfs tmpfs /tmp -o mode=700).  If change to any directory in /tmp I can 
no longer execute binaries that live on the root filesystem (nfs at this 
stage).  I've tried passing exec option to mount but it doesn't help.

Can anyone explain why I can't run any executables if I cd to /tmp (eg. 
cd /tmp && /bin/ls) ??
How can I fix this ?  I'm sure it's a mount problem.  BTW the root 
filesystem is readonly.

Thanks,
Brendan Simon.