We are able to open Composer and work around.
But View Mashup will always open up a blank page.
Is there something needs to be configured on IE 10.
We are running Thingworx 5.4
Does the blank page have any url? Or does it just stop loading? I tried reproducing your issue, but couldn't. Also, is there any specific reason for sticking with IE 10 and not updating to IE 11?
Please do open a support case at the PTC eSupport Portal (https://support.ptc.com/appserver/cs/portal/), so that we can quickly take a look at your system and resolve the issue.
I've created a support case for you -
Case Number #12488757