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We are running HP ALM v11.50.536.
ALM Platform Loader v11.50 32-bit 11.52.536.0

First off, QC is a 32-bit application, you must use the 32-bit Internet Explorer.
Then, you need to have the end users do a little IE configuring:

**Internet Explorer Configuration**

Before you download Application Lifecycle Management on a client
machine, you must perform the following configurations to the Internet
Explorer browser on the client machine.

* Configure the Custom Level security settings. The Custom Level security setting should be configured for the specific zone of the ALM Platform server.

* Set Internet Explorer as the default Web browser. This ensures that external links to ALM entities will open in ALM.

To configure security settings on the client machine:

1) In Internet Explorer, select Tools > Internet Options. The Internet Options dialog box opens.

2) Click the Security tab. The Web content zone of the ALM Platform server (Internet or Local intranet) is automatically selected. Click Custom Level.

3) In the Security Settings dialog box, configure the following settings. Under .NET Framework-reliant components:

* Set Run components not signed with Authenticode to Enable.

* Set Run components signed with Authenticode to Enable.

4) Under ActiveX controls and plug-ins:

* Set Run ActiveX controls and plug-ins to Enable.

* Set Download signed ActiveX controls to Enable or Prompt.

Note: You do not need to enable Download signed ActiveX controls if you
install the ALM client by using the HP ALM Client MSI Generator Add-in
on the More HP Application Lifecycle Management Add-ins page. This
allows you to install all ALM modules on a client machine without
downloading them through a browser.

a. **Add the ALM Platform server site to the Trusted Sites security zone.**

b. **Disable the Protected Mode for the Trusted Sites security zone (Windows Vista/7 default).**

5) Click OK

6) Then try to load the QC/ALM Client from the URL again.