Apparently ecc_decrypt clobbers its input (the cipher text to be decrypted). Here is a patch:

--- _pyecc.c~
+++ _pyecc.c
@@ -103,15 +103,16 @@
 ECC_State PyCObject \
 \n\
 ";
 static PyObject *py_decrypt(PyObject *self, PyObject *args, PyObject *kwargs)
 {
-    PyObject *temp_state, *temp_keypair;
+    PyObject *temp_state, *temp_keypair, *retval;
     ECC_State state;
     ECC_KeyPair keypair;
     ECC_Data encrypted;
     char *data;
+    char *dcopy;
     int datalen;

     if (!PyArg_ParseTuple(args, "s#OO", &data, &datalen, &temp_keypair,
             &temp_state)) {
         return NULL;
@@ -118,20 +119,28 @@
     }

     state = (ECC_State)(PyCObject_AsVoidPtr(temp_state));
     keypair = (ECC_KeyPair)(PyCObject_AsVoidPtr(temp_keypair));

+    if (!(dcopy = (char *)malloc(datalen))) { /* Make a copy of the encrypted input because ecc_decrypt is going to stomp on it */
+      Py_RETURN_NONE;
+    }
+
+    memcpy(dcopy, data, datalen);
+
     encrypted = ecc_new_data();
-    encrypted->data = data;
+    encrypted->data = dcopy;   /* Use the copy */
     encrypted->datalen = datalen;

     ECC_Data result = ecc_decrypt(encrypted, keypair, state);

     if ( (result == NULL) || (result->data == NULL) )
         Py_RETURN_NONE;

-    return PyString_FromStringAndSize((char *)(result->data), result->datalen);
+    retval = (PyObject *) PyString_FromStringAndSize((char *)(result->data), result->datalen);
+    free(dcopy);
+    return retval;
 }

 static char new_keypair_doc[] = "\
 Return a new ECC_KeyPair object that will contain the appropriate \
 references to the public and private keys in memory\n\

When I was trying to install pyECC in ubuntu 10.10 the following error was raised

building '_pyecc' extension
gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include -I/usr/local/include -I/usr/include/python2.7 -c seccure/libseccure.c -o build/temp.linux-x86_64-2.7/seccure/libseccure.o -Wall -Werror
gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include -I/usr/local/include -I/usr/include/python2.7 -c seccure/numtheory.c -o build/temp.linux-x86_64-2.7/seccure/numtheory.o -Wall -Werror
gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include -I/usr/local/include -I/usr/include/python2.7 -c seccure/ecc.c -o build/temp.linux-x86_64-2.7/seccure/ecc.o -Wall -Werror
seccure/ecc.c: In function ‘point_decompress’:
seccure/ecc.c:111:12: error: variable ‘rc’ set but not used [-Werror=unused-but-set-variable]
seccure/ecc.c: In function ‘pointmul’:
seccure/ecc.c:364:7: error: variable ‘rc’ set but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors

The following errors are generated while installing in mac 10.10.1 OS X
In file included from seccure/libseccure.c:32:
seccure/libseccure.h:20:9: error: 'LIBSECFURE_H' is used as a header guard
here, followed by #define of a different macro [-Werror,-Wheader-guard]

ifndef LIBSECFURE_H

    ^~~~~~~~~~~~~~

seccure/libseccure.h:21:9: note: 'LIBSECCURE_H' is defined here; did you mean
'LIBSECFURE_H'?

define LIBSECCURE_H

    ^~~~~~~~~~~~~~
    _LIBSECFURE_H_

seccure/libseccure.c:60:22: error: equality comparison with extraneous
parentheses [-Werror,-Wparentheses-equality]
if ( (keypair->pub == NULL) )
~~~~~~~~~~~~~^~~~~~~
seccure/libseccure.c:60:22: note: remove extraneous parentheses around the
comparison to silence this warning
if ( (keypair->pub == NULL) )
~ ^ ~
seccure/libseccure.c:60:22: note: use '=' to turn this equality comparison into
an assignment
if ( (keypair->pub == NULL) )
^~
=
seccure/libseccure.c:474:13: error: equality comparison with extraneous
parentheses [-Werror,-Wparentheses-equality]
if ( (data == NULL) ) {
~~~~~^~~~~~~
seccure/libseccure.c:474:13: note: remove extraneous parentheses around the
comparison to silence this warning
if ( (data == NULL) ) {
~ ^ ~
seccure/libseccure.c:474:13: note: use '=' to turn this equality comparison into
an assignment
if ( (data == NULL) ) {
^~
=
seccure/libseccure.c:682:13: error: equality comparison with extraneous
parentheses [-Werror,-Wparentheses-equality]
if ( (data == NULL) ) {
~~~~~^~~~~~~
seccure/libseccure.c:682:13: note: remove extraneous parentheses around the
comparison to silence this warning
if ( (data == NULL) ) {
~ ^ ~
seccure/libseccure.c:682:13: note: use '=' to turn this equality comparison into
an assignment
if ( (data == NULL) ) {
^~
=
4 errors generated.
error: command 'clang' failed with exit status 1

Instead of defaulting to the current curve (DEFAULT_CURVE) the ECC_Options structure should allow for the specifying of arbitrary curves.