2
The solution may be even simpler than that.
Go into System Admin »» Preferences Main »» General Settings and set "Update module template .html files from themes/your theme/templates directory?" to Yes.
Now, go into Modules Administration and click on the update button next to System. This recreates the system templates for your site.
Now see if your Main Menu block is there again. If not, do the following...
Go into Template Set Manager and click on the List link next to System.
In the next page you may see a row that is highligted in yellow. If it's the system_block_mainmenu.html row, you're in luck! Just click the Generate link and it will recreate your Main Menu template.
If the above doesn't work, simply download the version of XOOPS you have installed (i.e.: 2.0.13.2 or 2.2.3), extract the archive on your desktop, and upload the modules\system\templates\blocks\system_block_mainmenu.html file into the corresponding directory on the server.
Then just repeat the steps listed above.
Once you're done, go into System Admin »» Preferences Main »» General Settings and set "Update module template .html files from themes/your theme/templates directory?" to No.
Hope this helps.
James
Insanity can be defined as "doing the same thing over and over and expecting different results."
Stupidity is not a crime. Therefore, you are free to go.