302 endless redirect loop on checkout page

Hello,
Some of our clients experiencing the following issue: when some products is added to the cart and they try to checkout they get message that page is not redirecting properly. Below is log entries

[11/May/2015:17:55:08 +0100] "GET /index.php?route=checkout/cart HTTP/1.1" 302 - "http://mysiteurl.com/index.php?route=pr ... uct_id=572" "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0; BOIE9;ENUS)"
[11/May/2015:17:55:08 +0100] "GET /index.php?route=checkout/checkout HTTP/1.1" 302 - "http://mysiteurl.com/index.php?route=pr ... uct_id=572" "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0; BOIE9;ENUS)"
[11/May/2015:17:55:08 +0100] "GET /index.php?route=checkout/cart HTTP/1.1" 302 - "http://mysiteurl.com/index.php?route=pr ... uct_id=572" "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0; BOIE9;ENUS)"
[11/May/2015:17:55:09 +0100] "GET /index.php?route=checkout/checkout HTTP/1.1" 302 - "http://mysiteurl.com/index.php?route=pr ... uct_id=572" "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0; BOIE9;ENUS)"
[11/May/2015:17:55:09 +0100] "GET /index.php?route=checkout/cart HTTP/1.1" 302 - "http://mysiteurl.com/index.php?route=pr ... uct_id=572" "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0; BOIE9;ENUS)"
[11/May/2015:17:55:09 +0100] "GET /index.php?route=checkout/checkout HTTP/1.1" 302 - "http://mysiteurl.com/index.php?route=pr ... uct_id=572" "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0; BOIE9;ENUS)"
[11/May/2015:17:55:10 +0100] "GET /index.php?route=product/category&path=24_83 HTTP/1.1" 200 9069 "http://mysiteurl.com/index.php?route=pr ... ry&path=24" "Mozilla/5.0 (Linux; U; Android 4.1.2; el-gr; GT-I8190 Build/JZO54K) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30"
[11/May/2015:17:55:10 +0100] "GET /index.php?route=checkout/cart HTTP/1.1" 302 - "http://mysiteurl.com/index.php?route=pr ... uct_id=572" "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0; BOIE9;ENUS)"


Any help determining what is going on will be much appreciated