Hello,
I am sorry about the issue.
Could you please follow these steps and then check the situation again?

1) Close the software.
2) Go to C:\Users\YourUsername\AppData\Local\Incomedia\WebSite X5 - Pro
3) Enter the folder called PluginApps and delete the following subfolders:

24f3b39b-2e09-438d-b3b8-2f2e6b5102b
Cache
IconsCache
PreviewImagesCache

4) Enter the folder WebCache and delete all of its content.

After this, please try to place the object in a page again.

Eric