All content desappear

Are there any JavaScript errors?
Which browser did this happen in?
Have you tested with more browsers?
Which plugins have you enabled? Teaser Break, Image Assist?
Are the contents still there if you switch to another editor or click "Disable Rich-Text Editing"? If so, it's most likely not a problem with Wysiwyg module or the editor.
Which input filters have you enabled?
What kind of content did you test with?

Can you describe the page jumping in more detail? It might just be the editor detaching before content is submitted.

Are the contents still there if you switch to another editor or click "Disable Rich-Text Editing"?

- It works

Then it seems Wysiwyg module is working. The code which runs during the above operation and the one running when the form is submitted are nearly identical.
(The jumping problem does sound like an effect of the editor detaching. As the editor is taller than the original textarea, the contents below will shift up when they are swapped. Might be possible to get around by not doing a full detach on submit.)
If the contents are also there if you edit the node again, Wysiwyg module is definitly working as it should and you're seeing a rendering problem.

Which input filters have you enabled?

- Full HTML

Full HTML is an input format, I want to know which input filters are enabled on that format, which hints about which code is run by Drupal when the node is shown. (These are not controlled by or associated with Wysiwyg module, but might stop the viewed node from being rendered correctly.) Check this by clicking configure on admin/settings/filters.

No problem, I understand which filters you mean.

The linebreak filter should not be enabled when using WYSIWYG editors. The editors already take care of inserting <br /> and <p>...</p> tags where they are needed. And they might also use \n for formatting the source, so all those newlines will also be converted to <br /> and <p></p> tags when viewing the node/comment, making it look really weird.

We have also noted that the linebreak filter can cause content to not be rendered at all. See #602116: Long text is not rendered when viewing a node and #133188: Line break converter can result in empty node display - PCRE limits for more info on that.
If the content is still there when editing a node again, that seems like the most likely problem as the content has been properly saved to the databese but will not render after the filters have been applied when viewing a node.
Is the content still there when editing the node/comment?

If you already have a bunch of content using newlines instead of tag you might want to try something like #513998: Plugin to convert p- and br-tags to newlines, you'll be able to turn off that filter while not having to manually convert all that content.

Sorry, without further information this issue can only be marked as won't fix.

Feel free to re-open this issue if you want to provide further information. Thanks.