Question : Computer cannot access 1 particular website even after ipconfig /flushdns

This problem is only happening on 1 PC on our domain.  All other PC's can access this website just fine.  This particular machine cannot access www.site.com (fictitious).  We clear the dns cache, checked network connections and cleared internet history & cookies.  After we flush the dns, the website comes up perfectly and you are able to browse within the site.  However, the next day or so, the same PC cannot access the website.  I don't know what is wrong with this thing.  We clear the dns cache again and it works.  Only 2 days later:  SAME THING.  Please help.

Answer : Computer cannot access 1 particular website even after ipconfig /flushdns

Things you might ask/check:

Can it resolve at all when it has a problem?
What does nslookup tell you?
Does it have problems resolving any other sites?
Any events of note? Network issues?
Can you telnet to port 53 of the name server when there are problems?
Can you telnet to port 80 of the site name and/or the ip address of the site?
Are you using a proxy?
Are you using multiple DNS servers?
How many A records are there for this site?
Can this host access all of them?
Is it worth you or your companies time fixing this? Rebuild time perhaps?