Updating Caused Error, WordPress won't load now…

I apologize, I have no idea what version I was on – but I was trying to upgrade to 3.1.2

I remember something like this happened last time I attempted to upgrade wordpress on my site (and ever since then I’ve been terrified of upgrading because this was such a headache last time). Unfortunately, I don’t remember what I did to fix the problem. :/

Any aspect of my WordPress blog that I attempt to load now gives me this error message:

Warning: require(/home/saraqael/poro-poro.com/journal/wp-includes/default-constants.php) [function.require]: failed to open stream: No such file or directory in /home/saraqael/poro-poro.com/journal/wp-settings.php on line 20

Fatal error: require() [function.require]: Failed opening required ‘/home/saraqael/poro-poro.com/journal/wp-includes/default-constants.php’ (include_path=’.:/usr/local/lib/php:/usr/local/php5/lib/pear’) in /home/saraqael/poro-poro.com/journal/wp-settings.php on line 20

There is no file under journal/wp-includes/default-constants.php (er, as the error message says) and I’m not sure how I can go about fixing that. Any help would be greatly appreciated! ?? Thanks!

The site is https://www.poro-poro.com/journal/