It seems that bug #14142 is back.
This simple exemple generate a Segmentation fault.
The bug occurs only when RETURNTRANSFER is set and when using 2 curl_exec on the same curl handle.
Changing the 2nd URL to http://www.php.net/ generate an infinite loop !

<?
$ch = curl_init();
curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch,CURLOPT_URL,"http://www.apple.com/");
$res1 = curl_exec($ch);

curl_setopt($ch,CURLOPT_URL,"http://www.apple.com/quicktime/");
$res2 = curl_exec($ch);

curl_close($ch);
?>

PHP 4.2.2 / libcurl 7.9.8 and './configure --with-curl'.

Here is the back trace
Program received signal SIGSEGV, Segmentation fault.
0x080d580c in _efree (ptr=0x81a2164) at zend_alloc.c:222
222             CALCULATE_REAL_SIZE_AND_CACHE_INDEX(p->size);
(gdb) where
#0  0x080d580c in _efree (ptr=0x81a2164) at zend_alloc.c:222
#1  0x080e3c5e in _zval_dtor (zvalue=0x818d324) at zend_variables.c:44
#2  0x080dbf68 in _zval_ptr_dtor (zval_ptr=0x818d570) at zend_execute_API.c:274
#3  0x080e9a61 in zend_hash_destroy (ht=0x8155188) at zend_hash.c:541
#4  0x080dbcaa in shutdown_executor () at zend_execute_API.c:173
#5  0x080e4c7e in zend_deactivate () at zend.c:596
#6  0x080611da in php_request_shutdown (dummy=0x0) at main.c:787
#7  0x0806009b in main (argc=2, argv=0xbffff9e4) at cgi_main.c:827
#8  0x401db657 in __libc_start_main (main=0x805f7a4 <main>, argc=2, 
    ubp_av=0xbffff9e4, init=0x805e424 <_init>, fini=0x8107d40 <_fini>, 
    rtld_fini=0x4000dcd4 <_dl_fini>, stack_end=0xbffff9dc)
    at ../sysdeps/generic/libc-start.c:129