Is there any Virus protection software running on the user machine? If yes, I suggest user to uninstall McAfee/Virus protection software from the machine. After uninstall/Disable the McAfee software in the machine. I would request you to run the ALM Client Cleanup Tool on the machine. Once the cleanup process has completed, reboot the machine.
Once the machine is back up and running, open a 32-bit version of Internet Explorer as an admin (Right-click and run as administrator). If you don't have a 32-bit version of IE, you can find it under Program Files(x86) --> Internet Explorer --> iexplore.exe.
If above solution doesn't work, Please use the ALM explorer, The HP ALM Explorer Add-in enables you to use HP ALM without using a Web browser, such as Microsoft Internet Explorer. This is useful if user come across any issue with IE. I have uploaded the ALM Explorer to the case
Please refer below article which talks about specified cast is not valid.
KM00463358 -- Specified cast is not valid error in ALM Client
registry key should point to vbscript.dll
If above solution doesn't work then I suspect some corruption took place at memory/OS as it is impacting only a single user machine.
If reinstall of the operating system is an option for you, this may be a good suggestion as it would likely clear out any corruption issues that may be occurring.