You may need to define an alternate temp location with at least 150 meg of space for the 12.1 Web Viewer install.
To add a command line argument to define an alternate temp location for the install, the instructions are:
The System Property you will want to set is:
It can be included in the Web Viewer install command as:
java -Dlax.nl.env.iatempdir=<desired path>/tmp -jar CAOMWV.jar for r12.1