FWIW, I just had a series of "cannot connect" and threw a packet sniffer at it while it lasted. There's nothing going on but the browser sending (a total of four) SYNs, and promptly getting RSTs back:
00:25:20.552966 IP mylaptop.33297 > 198.91.81.5.80: Flags [S], seq 254282685, win 29200, options [mss 1460,sackOK,TS val 195881290 ecr 0,nop,wscale 7], length 0
00:25:20.669602 IP 198.91.81.5.80 > mylaptop.33297: Flags [R.], seq 0, ack 254282686, win 0, length 0
00:25:20.669901 IP mylaptop.33298 > 198.91.81.5.80: Flags [S], seq 3575710619, win 29200, options [mss 1460,sackOK,TS val 195881407 ecr 0,nop,wscale 7], length 0
00:25:20.783257 IP 198.91.81.5.80 > mylaptop.33298: Flags [R.], seq 0, ack 3575710620, win 0, length 0
00:25:20.783643 IP mylaptop.33299 > 198.91.81.5.80: Flags [S], seq 3057264016, win 29200, options [mss 1460,sackOK,TS val 195881521 ecr 0,nop,wscale 7], length 0
00:25:20.901366 IP 198.91.81.5.80 > mylaptop.33299: Flags [R.], seq 0, ack 3057264017, win 0, length 0
00:25:20.901585 IP mylaptop.33300 > 198.91.81.5.80: Flags [S], seq 3674252768, win 29200, options [mss 1460,sackOK,TS val 195881639 ecr 0,nop,wscale 7], length 0
00:25:21.017029 IP 198.91.81.5.80 > mylaptop.33300: Flags [R.], seq 0, ack 3674252769, win 0, length 0
Could be a firewall throttling traffic or the connection rate, or the server running out of sockets or file descriptors to accept the connection attempts ...