The ksh that ships with pre-2.8 versions of Solaris has a bug that causes ksh to hang during some actions including install operations. Avoid using the pre-2.8 Solaris ksh with nmake. The nmake package for Solaris ships with a replacement ksh. When you run nmake make sure the nmake bin directory (<nmake_root>/bin) is in your PATH before the system ksh. It is not enough to set SHELL=<nmake_root>/bin/ksh in your environment, the nmake ksh must be the first ksh in the PATH.
Sun has fixed the problem in Solaris 2.8! We have tested the ksh that is shipped with Solaris 2.8 and it does not exhibit any of the ill behavior we have seen with previous releases. If you are using Solaris 2.8 you are no longer forced to use the nmake provided ksh.
We also believe Sun has ksh patches available for other Solaris releases. If we find out details of the patch numbers we will post them here.