I was able to resolve the original issue with this fix:

includes/class/rss_feed.php
Find (line ~383):

Code:
if ($time == false || (time() - filemtime(DIR_FS_RSSFEED_CACHE . '/' . $zv_file)) < $time) {
Replace by

Code:
if ($time == false || (time() - filemtime(DIR_FS_RSSFEED_CACHE . '/' . $zv_file)) > $time) {
Now the RSS feed at least displays, but now I'm attempting to import the feed to Vbulletin and I get this error:

Abibitumi Kasa Store XML Error: not well-formed (invalid token) at line 3115

Any assistance would again be most appreciated.