Hi Cveti,

Since you ahave mentioned that the problem is not always and occurs randomly, you can try the below mentioned fixes to resolve this issue:

Fix 1: It's quite possible that simply pressing "F5" (or clicking the "Refresh" icon) could easily resolve your problem.
You can also try clicking the "Back" and "Forward" buttons.

Fix 2: Reset Internet Explorer settings
You can try resetting Internet Explorer settings to what they were when Internet Explorer was first installed on your PC. This can be useful for troubleshooting problems that may be caused by settings changed after installation. Note that resetting Internet Explorer isn't reversible, and all previous settings are lost after reset.

1. Close all Internet Explorer windows. Select the Tools button, and then select Internet options.
2. Select the Advanced tab, and then select Reset.
3. In the Reset Internet Explorer Settings dialog box, select Reset.
4. When Internet Explorer finishes applying default settings, select Close, and then select OK. Restart your PC to apply changes.

Fix 3: Run Internet Explorer in "No Add-Ons" mode
Internet Explorer add-ons, such as ActiveX controls and browser toolbars, are used by some Web sites to provide an enhanced browsing experience. An error may occur if an add-on is damaged or if an add-on conflicts with Internet Explorer. To determine whether the error is caused by an add-on, run Internet Explorer in "No Add-ons" mode.
You can open Internet Explorer without add-ons using the following step.

• Click start.
• Select All Programs
• Click Accessories
• Under System Tools
• Select Internet Explorer (no Add-ons).

Fix 4: Perform System Restore
In order to return to a previous state when your computer was functioning correctly use System Restore. It can also change Internet Explorer settings, scripts, batch files, and other kinds of executable files on your computer.
System Restore does not affect personal files, such as e-mail, documents, or photos.
To perform System Restore, follow the below points:

1. Log on to your computer as an administrator.
2. Open the Control Panel by clicking Start, and then clicking Control Panel.
3. Click System and Security, and then click System.
4. Under the Control Panel Home menu, click System protection.
5. Click System Restore.
6. Recommended Restore is the default choice. This restore is the most recent restore point and the best place to start.
7. To choose a different restore point, click Choose a different restore point, click Next and then click a restore point.
8. Click Next, and then click Finish to confirm your restore point.
9. To start the restore process, click Yes.
10. Once the system restore is complete, your computer will restart.

Then uninstall Adobe Flash player and then reinstall it by downloading the latest version from below link:

https://get.adobe.co....

Fix 5: It is possible that Internet Explorer has been selectively muted in the Volume Mixer.
To check this:
Open Internet Explorer, preferably to a page that should be playing some sound.
Click on the volume icon in the windows system tray (in the right-hand lower corner of the taskbar), and then click on the link labeled "Mixer".
A panel will open showing the individual volume levels of all running apps that play sounds (you may need to scroll to the right to see all of them).
Make sure that the volume level belonging to Internet Explorer is not set to mute.

I hope this helps in fixing the videos and audio issue on YouTube.

Regards,
Lokesh