Intermittent 500 errors in apache default-access.log file

[Srikanth]

Line 106747: 1.127.42.154 - - [21/May/2013:12:00:20 +1000] "GET /news/bell-helicopter-sale-by-tender HTTP/1.1" 500 20 982901 "-" "www.tollgroup.com"
Line 112722: 203.45.151.57 - - [21/May/2013:12:16:17 +1000] "GET /news/bell-helicopter-sale-by-tender HTTP/1.1" 500 20 841734 "-" "www.tollgroup.com"
Line 113221: 203.45.151.57 - - [21/May/2013:12:17:28 +1000] "GET /news/bell-helicopter-sale-by-tender HTTP/1.1" 500 20 634052 "-" "www.tollgroup.com"
Line 113795: 203.45.151.57 - - [21/May/2013:12:18:40 +1000] "GET /news/bell-helicopter-sale-by-tender HTTP/1.1" 500 20 674401 "-" "www.tollgroup.com"
Line 115275: 203.30.95.20 - - [21/May/2013:12:23:58 +1000] "GET /news/bell-helicopter-sale-by-tender HTTP/1.1" 500 20 606635 "-" "www.tollgroup.com"
Line 115858: 203.45.151.57 - - [21/May/2013:12:25:26 +1000] "GET /news/bell-helicopter-sale-by-tender HTTP/1.1" 500 20 3101729 "-" "www.tollgroup.com"
Line 116402: 203.45.151.57 - - [21/May/2013:12:26:48 +1000] "GET /news/bell-helicopter-sale-by-tender HTTP/1.1" 500 20 786623 "-" "www.tollgroup.com"
Line 118289: 203.30.95.20 - - [21/May/2013:12:33:42 +1000] "GET /news/bell-helicopter-sale-by-tender HTTP/1.1" 500 20 681963 "-" "www.tollgroup.com"


Will appreciate any help.

[Altrea]

Contents of your apache error.log and php php_error file?