no internet access (windows works)

[phileas]

I had a router Fritz!Box phone 7170. There was a problem with the router and I bought another Fritz!Box 7170. I tried to access the router by using http://192.168.178.1/ and to configure it, using my linux mint PC. After the configuration (internet works) it is not possible for my Linux mint PC to connect to the internet. I checked my network settings, DHCP is used. Skype works, internal connection with my windows machines works, FireFox and Thunderbird don't work. The connection is not possible neither with cable nor with wifi.

Can someone help me?

[phileas]

ifconfig
eth0 Link encap:Ethernet HWaddr a0:b3:cc:ce:1c:e7
inet addr:192.168.178.26 Bcast:192.168.178.255 Mask:255.255.255.0
inet6 addr: fe80::a2b3:ccff:fece:1ce7/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:928 errors:0 dropped:0 overruns:0 frame:0
TX packets:1623 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:134110 (134.1 KB) TX bytes:175706 (175.7 KB)
Interrupt:41 Base address:0xe000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:218 errors:0 dropped:0 overruns:0 frame:0
TX packets:218 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:6694 (6.6 KB) TX bytes:6694 (6.6 KB)

wlan0 Link encap:Ethernet HWaddr 44:6d:57:43:ad:c1
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)