php error wcache.class.php on line 291

i’m using latest version of plugin …can you please give advice on how to fix these errors?

[06-Mar-2014 13:22:08 UTC] PHP Warning: flock() expects parameter 1 to be resource, boolean given in /wp-content/plugins/wp-widget-cache/inc/wcache.class.php on line 291

[06-Mar-2014 17:41:47 UTC] PHP Warning: filemtime() [function.filemtime]: stat failed for /server/wp-content/widget-cache/mysite.com/6e2d012a87bd69e58b13107dfba35839/aaf4f24559de99cc0bd5843057d8da34 in /server/web/content/wp-content/plugins/wp-widget-cache/inc/wcache.class.php on line 315

https://www.ads-software.com/plugins/wp-widget-cache/