600 seconds means 10 mins. Try to increase this because generally this happens if server time and local time mismatch or simple words, the server time is not correct. Sometimes it happens due to difference in server time and your computer's local time.
For example, if difference between your computer and server computer is more than 10 minutes, then cookie will not set properly in IE yet it will work on Firefox. So try to set cookie as follows:
setcookie('counter',1,time()+3600,'/');