Petr,
I've begun to get random failures on uploads for both HamQTH and HRDLog.  I ran a manual upload to HamQTH while i issued a continous ping to hamqth.com.  Although the upload failed, there were no ping drops.  See details below:
 
HamQTH: Uploading FG4NOHamQTH: Upload failed! Check Internet connection
--- hamqth.com ping statistics ---221 packets transmitted, 214 received, 3% packet loss, time 220070msrtt min/avg/max/mdev = 312.599/324.112/483.309/13.377 ms
HRDLog: Uploading 9H5G/C6AHRDLog: Upload failed! Check Internet connection
--- hrdlog.net ping statistics ---230 packets transmitted, 225 received, 2% packet loss, time 229076msrtt min/avg/max/mdev = 285.271/292.028/305.291/2.896 ms