Memory exhausted in AllocSetAlloc()

Hey everybody,
whenever I do a 'select * from profil_ext2;' I get

FATAL 1:  Memory exhausted in AllocSetAlloc()
pqReadData() -- backend closed the channel unexpectedly.
        This probably means the backend terminated abnormally
        before or while processing the request.
The connection to the server was lost. Attempting reset: Succeeded.

Now, I read the manual and I know that one can use ulimit to increase
the size of virtual memory. But with ulimit -a I get the following
listing:
core file size (blocks)  1000000
data seg size (kbytes)   unlimited
file size (blocks)       unlimited
max memory size (kbytes) unlimited
stack size (kbytes)      8192
cpu time (seconds)       unlimited
max user processes       2048
pipe size (512 bytes)    8
open files               1024
virtual memory (kbytes)  2105343

And I think 2105343 kbytes is fairly enough virtual memory.

Any suggestions on what I can do?

Thomas