Malloc returns 0x100000000

I have a strange problem with malloc. After allocating <10mb with several mallocs, malloc suddenly returns the address 0x100000000that SIGSEGV calls upon access. I have no idea what is wrong. The parameter is errnoset to value 0, and I have enough space in ram, so this should not be a space problem. The last addresses returned by malloc were less than 0x6255f0. Any idea what to look for?

Some information about my system:

• gcc version 4.4.5 (Ubuntu / Linaro 4.4.4-14ubuntu5)
• flags: -Wall
• uname: 2.6.35-27-generi # 48-Ubuntu SMP Tue 22 Feb 20:25:46 UTC 2011 x86_64 GNU / Linux

PMAP Output:

Address           Kbytes     RSS   Dirty Mode   Mapping
0000000000400000       0      32       0 r-x--  tests
000000000060a000       0       4       4 r----  tests
000000000060b000       0       4       4 rw---  tests
000000000060c000       0     116     116 rw---    [ anon ]
00007ffff75cd000       0     348       0 r-x--  libc-2.12.1.so
00007ffff7747000       0       0       0 -----  libc-2.12.1.so
00007ffff7946000       0      16      16 r----  libc-2.12.1.so
00007ffff794a000       0       4       4 rw---  libc-2.12.1.so
00007ffff794b000       0      12      12 rw---    [ anon ]
00007ffff7950000       0      32       0 r-x--  libm-2.12.1.so
00007ffff79d2000       0       0       0 -----  libm-2.12.1.so
00007ffff7bd1000       0       4       4 r----  libm-2.12.1.so
00007ffff7bd2000       0       4       4 rw---  libm-2.12.1.so
00007ffff7bd3000       0      28       0 r-x--  liblinopt.so
00007ffff7bdb000       0       0       0 -----  liblinopt.so
00007ffff7dda000       0       4       4 r----  liblinopt.so
00007ffff7ddb000       0       4       4 rw---  liblinopt.so
00007ffff7ddc000       0     108       4 r-x--  ld-2.12.1.so
00007ffff7f6c000       0     432     432 rw---    [ anon ]
00007ffff7ff8000       0      12      12 rw---    [ anon ]
00007ffff7ffb000       0       4       0 r-x--    [ anon ]
00007ffff7ffc000       0       4       4 r----  ld-2.12.1.so
00007ffff7ffd000       0       4       4 rw---  ld-2.12.1.so
00007ffff7ffe000       0       4       4 rw---    [ anon ]
00007ffffffde000       0      16      16 rw---    [ stack ]
ffffffffff600000       0       0       0 r-x--    [ anon ]
----------------  ------  ------  ------
total kB            9160    1196     648

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7bd8e67 in bound_knapsack (sizes=0x610b30, profits=0x610ad0, B=103, 
    limit=2) at /home/x/Development/binpacking/src/lib/knapsack.c:123

UPDATE

valgrind : calloc : calloc( n, sizeof(unsigned int)); : calloc( n, sizeof(unsigned int*)); , malloc.

!