Maximum Transmission Unit (MTU) is the maximum packet size, in bytes, that can be transmitted across a link. The MTU determines the size of your packets, so if it is too small, your computer will be responding often. If it is too big, errors will cause each packet to be resent. But this pertains just to what is happening between your router and your laptop. Since I assume you are using your laptop in the same proximity to your router both in the AM and in the afternoon and evenings, then I can see no relationship to the MTU. If your router has transmission frequency choices, try going to another frequency (or channel). Could be that there are other's in your neighborhood using the same channel. Most units default to the same channel out of the box. You can use the software that came with the unit to reconfigure to another channel. Most routers will also have some sort of status display viewable using the software that came with it. That status display should tell you the vital signs of your link. You could look at this in the AM when things are working and look at the SEND and REC fields to see the number of successful or dropped packets that have been sent or received (some packet loss is to be expected in wireless networking). Then, look at the same fields FROM THE SAME LOCATION in the afternoons and evenings when you are having problems and compare the two. This will tell you if the problem is in your wireless hook up or outside on the Internet (or perhaps in your PC's software). If you see no substancial difference in the AM as compared to the troubled times, then it's not the router. Don't forget to check to be sure that you have the latest firmware downloaded from Linksys for your particular router. They do have upgrades from time to time.
Unsolved 
