Nope, firefox and no particular add-ons. I'll see if I can find out what's going on by analyzing the traffic when I have the time. 

217.115.41.218 - that's me! Don't know what I have done that is considered malicious, though.
Is the block time limited? I actually succeed in seeing the sensors from time to time.
Thanks again for your site - very useful.

I have also had problems to connect for a couple of weeks - but only intermittently
Attaching tracert log made when I can not connect.

Tracing route to www.tellmon.net [79.161.150.134]
over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms 192.168.254.90
2 <1 ms <1 ms <1 ms dr-se-sto-kn5-2-vl452.bredband2.net [217.115.41.217]
3 1 ms 1 ms 1 ms cr-se-kista-esbogatan11-1-be2.bredband2.net [82.209.176.141]
4 41 ms 1 ms <1 ms ae3.stk10.ip4.gtt.net [77.67.82.1]
5 1 ms <1 ms <1 ms xe-2-3-0.stk30.ip4.gtt.net [89.149.183.250]
6 5 ms <1 ms <1 ms as3549.ip4.gtt.net [77.67.82.146]
7 1 ms 1 ms 1 ms ae10.csr1.ARN3.gblx.net [67.17.74.41]
8 1 ms 1 ms 1 ms po6-60G.ar2.ARN3.gblx.net [67.16.146.82]
9 9 ms 11 ms 11 ms altbox.tengigabitethernet4-4.ar2.arn3.gblx.net [209.130.172.58]
10 37 ms 34 ms 44 ms 237.79-160-112.customer.lyse.net [79.160.112.237]
11 31 ms 31 ms 31 ms 2.79-160-49.customer.lyse.net [79.160.49.2]
12 37 ms 36 ms 36 ms 65.79-160-49.customer.lyse.net [79.160.49.65]
13 33 ms 33 ms 33 ms 203.79-160-49.customer.lyse.net [79.160.49.203]
14 * * * Request timed out.
 :
30 * * * Request timed out.

Trace complete.