Haven’t done much with SSI in awhile, but there’s nothing special about the Apache that is installed on an InterWorx box that would make it “not SSI friendly”.
From the Apache cookbook (and probably somewhere in the Apache docs too):
Note that Options IncludeNoExec, in addition to disabling the #exec SSI directive, also forbids the inclusion of CGI programs using the #include virtual syntax.
So that would explain why IncludesNoExec won’t let you #include a PHP file.
Try setting it back to “Options +Includes” and check the permissions on the rightmenu.shtml file. See if doing the following fixes the problem:
I have looked at every SSI thread on this forum and have tried all the tricks and its still not working right. Should I open a trouble ticket maybe?
Anyway it seems to be a “nesting” issue, on cPanel the client was able to “nest” SSI calls if they included an shtml page, but nesting doesn’t seem to work at the moment.
At the same time I don;t get why the pages calling php gp blank when set to Options +Includes but will show up with errors when set to Options +IncludesNOEXEC. Very weird stuff.