You can see what version of PHP we're running by looking in the AdminCP (I think. I can't remember. Unrepentant was the last site I used vBulletin on for obvious reasons. They really went to shit since the last time I used them).
You can also upload a php file to the server with
<?
phpinfo();
?>
I highly doubt Shawn will downgrade PHP to 5.3 from 5.4, as that has the potential to compromise the security of the other websites he hosts on that same server... When you require things like that, you're better off getting a virtual server and spinning up your own setup, since at this point you're now requiring a specialized setup.
The bottom line with the issues we're seeing with the Editor (Blank edit boxes, and Enter not working on the newest IE on Windows 8), is that it's all related to an older version of ckeditor thats built into vbulletin. Since the dev team is working on vb5, they haven't found the need to update the vb4 code with an updated ckeditor.
You have really 4 choices to fix this issue:
1. Hire/Find someone who can update the ckeditor code in our vbulletin to the latest version that doesn't have these issues. IF your lucky, someone may have allready done the work for us, and we can just buy it off them pre-packaged. Look on vbulletin.com and vbulletin.org.
2. Upgrade to vbulletin 5. Apparently all of these issues are fixed. The theme SHOULD be able to be ported over, as there aren't a lot of template differences. Might need to work on finding or porting some of the plugins. A warning though; vbulletin 5 hasn't been taken very well by the community. It might be time to move on.
3. Consider going with a new backend instead of vbulletin (I know, it's only been a year, but new web technology is coming out every day now). vBulletin is very resource heavy, so it could be a good reason to switch. It also seems that with the corporate buyout of vbulletin by internet brands, it's support has gone to shit and alot of big sites are jumping ship over to invision power board or Xenforo. Xenforo seems to be what many people are jumping too since a few of the old school good vbulletin developers(Including the founder of vbulletin.org) are the founders of Xenforo. Xenforo is also cheaper.
4. Disable the advanced editor all together and just use the very basic editor supplied with vbulletin.