You can use inline::C to provide test/demo scripts that we can all run (if Inline::C is installed).
The following runs fine for me on both perl-5.8.9 and perl-5.10. Do you still get the crash ?

use warnings;
use Inline C => Config =>
    BUILD_NOISY => 1;

use Inline C => <<'EOC';

void call_Subtract(int a , int b) {
        dSP;
        int count;

        ENTER;
        SAVETMPS;

        PUSHMARK(SP);
        XPUSHs(sv_2mortal(newSViv(a)));
        XPUSHs(sv_2mortal(newSViv(b)));
        PUTBACK;

        printf("PL_errgv2 = %p\n", PL_errgv);

        //count = call_pv("Subtract", G_EVAL|G_SCALAR);
        count = call_pv("Subtract", G_SCALAR);

        SPAGAIN;

        printf("PL_errgv3 = %p\n", PL_errgv);

        /* Check the eval first */
        if (SvTRUE(ERRSV))  /* crashes here */
        {
            STRLEN n_a;
            printf ("Uh oh - %s\n", SvPV(ERRSV, n_a));
            POPs;
        }
        else
        {
            if (count != 1)
               croak("call_Subtract: wanted 1 value from 'Subtract', g
+ot %d\n",
                        count);

            printf ("%d - %d = %d\n", a, b, POPi);
        }

        PUTBACK;
        FREETMPS;
        LEAVE;
    }


EOC

call_Subtract(25, 12);

sub Subtract {
    my $ret = $_[0] - $_[1];
    return $ret;
}
[download]

It ouptuts, for me:

PL_errgv2 = 002E3F20
PL_errgv3 = 002E3F20
25 - 12 = 13
[download]

Cheers,
Rob