It sounds to me like you have a DNS problem.
Check if your router uses automatic assigned IP addresses and DNS servers.
If so, change the DNS server to Google or OpenDNS - 8.8.8.8 -8.8.4.4 for Google, 208.67.222.222 -208.67.220.220 for OpenDNS.
Not sure how to clean the DNS cache on the tablet but if you forget your network connection and set it up with a fixed IP and DNS it should work.
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