Ken, Thanks for your help! Yes, I'm using WeatherLink software. At times, the WLtags.php file uploads fine (around 7.4 KB size) , and other times it uploads an empty (0 KB) file. I'm not sure what the issue is with the uploads. I tried setting up Weather-Display tonight, and it would only occasionally upload as well.
I've had an issue similar to this a couple of times before, where everything is working fine (uploads every 5 minutes) and then I'll get the intermittent upload issues. I've rebooted my PC, the router, and modem multiple times with no relief for the past 2 days. It usually starts working again after a few days. I have no issues at all when transferring via filezilla. I even tried Fling yesterday and it wouldn't work consistently either. I may try the WLtags-new.php file and see if anything changes.
Thanks again!