I'm using TTM since some years ago without issues. It works very well and is useful if a user want try an app. for some days and after to revert the system. Also I use it even with TTFreeze on and none issues.

Using Win 7.

Never had such warning (Warning: selected invalid function), however.

  ~ Freeware ~

Surfing:
- For surfing 'SecuBrowser' is an option [works with IE and Firefox only]. It is not so strong like SandboxIE, but does the work; I installed it in some friends PC's that had problems with some Ransomware and it handle with them well. I moved their sandboxed folder to a RamDisk with a junction in original folder, between others changes in default instalation.

Trying out programs:
-  Applications that don't need to reboot - 'Toolwiz Time Freeze' is an excellent choice.
-  Applications that need to reboot - 'Toolwiz Time Machine' is a very good way; it is stable and in a non-beta state now. It has also a Time Freeze feature.

Analyzing programs:
- Using 'System Explorer'; their snapshot feature is useful and does the work.

Anyway: If you buy SandboxIE you are doing a very good choice and purchase/acquisition indeed!