I was having this issue as well but I believe that I have fixed it. I tracked the problem down to the transient feed cache. It seems that when the plugin sets the cache timeout to 0 on line 26, it causes a problem with the transients never being garbage collected. I changed this line:
add_filter( 'wp_feed_cache_transient_lifetime', create_function( '$a', 'return 0;' )); // To reduce cache time
and set it to 60 seconds:
add_filter( 'wp_feed_cache_transient_lifetime', create_function( '$a', 'return 60;' )); // To reduce cache time
Then I went into the wp_options
table in my wordpress database and deleted all the old transient feeds:
DELETE FROM wordpress.wp_options WHERE option_name LIKE '_transient%_feed%';
Now when I refresh the page, it seems to be working now.