[2015-02-13 00:03:06 - hhh] The connection to adb is down, and a severe error has occured.
[2015-02-13 00:03:06 - hhh] You must restart adb and Eclipse.
[2015-02-13 00:03:06 - hhh] Please ensure that adb is correctly located at 'F:\android\android-sdk\platform-tools\adb.exe' and can be executed.
Although location is right
Here's a check list I used to do when I had problems like this. Nowadays, I use Android Studio and find I run into these kinds of issues far less often.
EDIT: Follow the links provided by Josef in the comment he/she responded to you with.