Its sounds strange for me duo we have the hole C-net. I have hard to believe that they have blocked a hole B or A-net?!
Your ISP might not like multiple ip answer? A nslookup should give your this anwser:
nslookup download.lavasoft.de
Server: 10.0.1.2
Address: 10.0.1.2#53
Non-authoritative answer:
download.lavasoft.de canonical name = dlserver.download.lavasoft.com.
Name: dlserver.download.lavasoft.com
Address: 82.99.19.11
Name: dlserver.download.lavasoft.com
Address: 82.99.19.12
Name: dlserver.download.lavasoft.com
Address: 82.99.19.13
Name: dlserver.download.lavasoft.com
Address: 82.99.19.14
Name: dlserver.download.lavasoft.com
Address: 82.99.19.15
Name: dlserver.download.lavasoft.com
Address: 82.99.19.16
Name: dlserver.download.lavasoft.com
Address: 82.99.19.17
Try to ping them or pick one of them and add /public/wu.dat in your web browser.
And no, have have not block you from the download servers
