I can't access some websites ... why?

I have this same issue. I can access a site and then 20 minutes later its not found. I know there is nothing wrong with my machine or the site. Because i can still visit other sites. I can use another computer to visit the site or use anonymizer sites to visit the site...so what is the actual issue here?

Thanks Leo,
I ran into this problem when I rearranged my home network through my Linksys Wireless Router. I used to connect the ICS host (internet connection sharing) through the router via wireless connection but now plugged in an ethernet cable. And since then had problem om my wireless laptop. Other sites also suggested this was a Linksys problem and might have to replace it. But you solved it. Many thanks!

when i open up Dr TCP in the MTU there is nothing in the box. I uninstalled msn messenger rebooted and everything works

It is not your MTU, it is your HOST script in Windows..To fix this go to:
c:/Windows/System32/drivers/etc/Hosts
You might find someone has changed your settings causing a loopback... This is all you should see in your HOST script..

This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host

127.0.0.1 localhost
::1 localhost

If for some reason there is anything else just delete it and save!! If you are using Vista you must access this file as an admin or change your privelages...Hope this helps some people!!!

Thank you so much, Jaco!!!!!! I have been trying to solve this problem for years! In fact, today I called my antivirus program manufacturer and complained that its product was blocking me from seeing some Web sites. They had me disable my antivirus and I still couldn't access the sites!

After reading your response, I checked my Hosts file, and, lo and behold, there were hundreds of entries placed in there!!! The culprit? Spybot Search and Destroy!

I removed all the entries, saved my hosts file, and Viola! I can access all the web sites that I couldn't before.

Again, many thanks!!!!

Many Thanks, I ended up just deleting the hosts file (after making a copy of it - just in case).
Then I could access all sites including Google.

I've tried what it suggest by altering the MTU, but still doesn't solve my problem from login into a forum and game website which i been login in for 2 years. the websites are as follows : engforum.lastchaos.com.my & www.lastchaos.com.my . i've tried on other PC and it works fine. I've even tried ping both of the websites and it replies as normal. i just couldn't access it through my internet browser. whenever i typed it on the address bar, it just keep waiting for page to load and in turn fail to load. hope there is someone who could help.

Super advice!!! Thank you so much. After tearing my LAN apart, disconnecting routers, switching out modems and spending two hours on the phone with my ISP tech support I was awaiting a site techs arrival. I found your site by accident, checked on a whim and discovered all MTU's were set to 0.
I reset them to 1500 and the results were amazing
I can now access sites I have been unable to get onto for months.

I'm experiencing a problem accessing ANTIVIRUS websites, I,ve visited a lot of forums for a possible solution, I tried to scan my computer with antimalware, antispyware and antivirus on safe mode, deleted all files on "Temp" folder, but still I cant access antivirus sites, i dont know if theres still a virus/malware lurking in my CPU or its just a setting that was changed by that virus, funny thing is only antivirus sites is one I cant access, (AVG, Avast, Symantec, kaspersky, Avira, PAnda, nod32, bitdefender,Norman.....etc)I'm actually using AVG 8, now my AVG's virus database is outdated since I cant update it, I used Avira, SuperAntispyware and Malwarebytes to scan in SafeMode, things are going fine, scanned some malware, cookies and virus, not I think its already clean and Zero Virus, but when I tried to access those said sites.... theres no luck, still I cant access Antivirus Sites, Pls help! thanks in advance!

Hi there im currently running on windows vista i am having trouble going on to websites ive been on before (days ago) i can log onto them from another website so i know there is no problem at there end and ive downloaded the drtcp but it comes up blank and too be honest not really sure what im doing :{. Does anyone know what this could be? thanks