From what i can see, the sites that you cannot access are not full addresses... ie
www.address.com instead of
www.address.com/index.html
Problem is, in the examples you have given i haven't been able to work out what the full address is. This leads me to believe that it may be a problem with framed forwarding, or some kind of similar method which means that you cannot access the site using the document name at the end of the url. I may be way of the mark with this... but if it is something that you investigate.
When you say that you cannot access the sites, i assume you mean that you get page cannot be displayed?
I seriously doubt that it is a flash issue as
this link that you gave as a not working example doesn't use flash at all.
can you access
http://home.wanadoo.nl ? if not, trying telnetting this site on port 80... to do so:
start -> run -> telnet
then type "open home.wanadoo.nl 80" (no quotes) [i can't remember if it works this way on XP or has the NT version where you have to chose Connect -> remote on the menus the type host name and port number]
when it shows you a blank window with a cursor type " get /" (it probably won't show when you type)
It should either stream html or flash up and then disconnect...
If you can think of a site where you can test the framed forwarding theory then that might be the easiest place to start. Also try disabling your firewall and then see if you can access the links so that you can rule that out as causing a problem.
hth
MB