Persistent, maddening DNS error since upgrading to Win 7

I have a Linksys WRT160NL wireless router, and cable internet access, and a Toshiba Satellite E105-S1602 laptop. I managed to set up my wireless network fine, and it works about 75% of the time (100% of the time with all my non-Windows 7 devices). The problems started when I "upgraded" from Windows XP to Windows 7. Before then, all was well, but since I switched, I get these persistent DNS problems. Every few hours on my Windows 7 Toshiba laptop, usually if I let it go to sleep and then restart it, but sometimes just randomly, I lose internet access and IE/Windows diagnostics says it's a DNS problem - basically that my connection can't contact the DNS.

I have played around and found that it works best when I set my connection to use a particular DNS address (provided by my cable company) rather than letting it find the DNS itself. I have also found it best to disable Internet Protocol V6 and just use IP V4. Despite this, I am losing internet access a couple of times a day. Is anyone able to give me any advice? I'm at my wit's end.

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