I found something else on the spot.


The following highlighted code just occurs in the "corrupted" header page, but I don't know what it means:


<td align="right" class="main" valign="top"><a href="/zenc/zcadmin/email_welcome.php? securityToken=XXXXXXXXXXXXXXXXXXXXXXXX&language=en&vcheck=yes"><img src="includes/languages/english/images/buttons/button_check_new_version.gif" border="0" alt="Check for Updates to Zen Cart" title=" Check for Updates to Zen Cart "></a><br />(You are presently using: v1.3.9h)</td>

The others (with the header OK) don't have that red part.

What's that? (I omitted it, because I don't know if it is some kind of password...)