Hi, its very rare
I contacted the domain provider, ovh where i have 2 domains

rta.cat and taxis.cc both with similar DNS, both @ to above mentioned IP

now using ping.eu/ping you can see

--- PING rta.cat (60.210.131.73) 56(84) bytes of data. ---
--- rta.cat ping statistics ---

packets transmitted  9
received  0
packet loss  100 %
time  8021 ms
 

VERSUS

--- PING taxis.cc (62.210.131.73) 56(84) bytes of data. ---
64 bytes from 62.210.131.73: icmp_seq=1 ttl=116 time=28.6 ms
64 bytes from 62.210.131.73: icmp_seq=3 ttl=116 time=28.9 ms
64 bytes from 62.210.131.73: icmp_seq=4 ttl=116 time=28.7 ms
64 bytes from 62.210.131.73: icmp_seq=5 ttl=116 time=28.6 ms


--- taxis.cc ping statistics ---

packets transmitted  5
received  4
packet loss  20 %
time  4009 ms
 

A look t DNS setting on domain provider

.taxis.cc
NS
ns14.ovh.net
.taxis.cc
NS
dns14.ovh.net
.taxis.cc
MX 1
redirect.ovh.net
.taxis.cc
A
62.210.131.73
www.taxis.cc
CNAME
taxis.cc

AND NOW RTA.CAT

.rta.cat
NS
ns100.ovh.net
.rta.cat
NS
dns100.ovh.net
.rta.cat
MX 1
aspmx.l.google.com
.rta.cat
MX 10
aspmx3.googlemail.com
.rta.cat
MX 10
aspmx2.googlemail.com
.rta.cat
MX 5
alt2.aspmx.l.google.com
.rta.cat
MX 5
alt1.aspmx.l.google.com
.rta.cat
A
60.210.131.73
www.rta.cat
CNAME
rta.cat
_jabber._tcp.rta.cat
CNAME
_jabber._tcp.redirect.ovh.net
_sip._udp.rta.cat
CNAME
_sip._udp.redirect.ovh.net
_xmpp-client._tcp.rta.cat
CNAME
_xmpp-client._tcp.redirect.ovh.net
_xmpp-server._tcp.rta.cat
CNAME
_xmpp-server._tcp.redirect.ovh.net
audio.rta.cat
CNAME
audio.ovh.net
bgeg5hujltk3roth54eeb7nhtpvn6l 67._domainkey.rta.cat
CNAME
bgeg5hujltk3roth54eeb7nhtpvn6l 67.dkim.amazonses.com
email.rta.cat
CNAME
ghs.google.com
ftp.rta.cat
CNAME
rta.cat
ftp2.rta.cat
CNAME
anonymous.ftp.ovh.net
imp.rta.cat
CNAME
imp.ovh.net
jabber.rta.cat
CNAME
jab1.redirect.ovh.net
mail.rta.cat
CNAME
ghs.google.com
ox.rta.cat
CNAME
ox.ovh.net
pop3.rta.cat
CNAME
ns0.ovh.net
sip.rta.cat
CNAME
sip1.redirect.ovh.net
smtp.rta.cat
CNAME
ns0.ovh.net
squirrel.rta.cat
CNAME
squirrel.ovh.net
tdnkuoash5sfjbvhhmrdu7qvyj5ki dzv._domainkey.rta.cat
CNAME
tdnkuoash5sfjbvhhmrdu7qvyj5ki dzv.dkim.amazonses.com
uhcudugrq3jz27tcyo5nlwrfpu5yf oao._domainkey.rta.cat
CNAME
uhcudugrq3jz27tcyo5nlwrfpu5yf oao.dkim.amazonses.com
vpn.rta.cat
CNAME
vpn.redirect.ovh.net
.rta.cat
SPF
v=spf1 a mx include:spf.mandrillapp.com ?all
_amazonses.rta.cat
TXT
eX+xGDrmkVMMFTuYXCeTmI/n 6sBaQNFaTSJNzS5r6ts=
mandrill._domainkey.rta.cat
TXT
v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQ UAA4GNADCBiQKBgQCrLHiExVd 55zd/IQ/J/mRwSRMAocV/hMB3j XwaHH36d9NaVynQFYV8NaWi69 c1veUtRzGt7yAioXqLj7Z4TeEUo OLgrKsn8YnckGs9i3B3tVFB+Ch/ 4mPhXWiNfNdynHWBcPcbJ8kjEQ 2U8y78dHZj1YeRXXVvWob2OaK ynO8/lQIDAQAB;

I still have confusion about your problem GOODYES, you said you had dns problem when you migrated from win server 2003 to 2008 r2.  that's make me think if you have this problem on win server 2008 instead of 2003.  if so, i think you need to check your 2003 server configuration and try to keep it compatible with 2008.

In my opinion, dns server will work if you got correct configuration between your ip address and dns server name.  that configuration might existed in host file, maybe you need to check your domain provider for solution....

Ping your domain www.rta.cat is no problem so I can only suggest you double check your network configuration on your new server 2008...

Hope that works!