Cazadero,   Try scanning for Malware? Download Malwarebytes Anti-Malware update it and do a quick scan.   Some Web sites may not behave as expected in Internet Explorer   How to reset Internet Explorer settings     Rick      
  I have a Dell 531s Inspiron desktop computer.  It is running  preinstalled Vista Home Premium 32 bit;  IE 8  and  Norton 360. On some, but not all, websites I cannot logon.  I enter my username and password and press Logon  -  but I keep being looped back to the logon screen.  Sometimes the error msg is " Your session has timed out.  Log in again."  or  "Invalid user name and/or password."  I have checked my logon info and it is correct. Oddly enough, on certain sites (e.g., WildBlue.net, my Internet Provider) I can logon through "My Account,"  but not through the "Customer Portal."  Once logged on to the website I still get looped if I try to logon to the "Home Page/Customer Portal." It seems to happen more often on (small ?) sites like Mercola.com, Lowes.com, WildBlue.net....   I can sign on to major websites like Amazon, eBay, PayPal, CitiCard, Discover, Wells Fargo, Kaiser....  just fine. For a long time I thought the glitch was in the website itself.  Now, after a number of website managers have tried without success to recreate the error, I suspect the glitch is in in my computer. Help please  -  I have spent many hours searching and trying to fix this glitch  -  any suggestions would be much appreciated.   
Website Logon Caught in an Infinate Loop