I can reproduce the problem on any graphics driver (including vesabios and svga) in QNX 6.4.1 and in any 32 bpp video 
mode, but only with these alpha blending flags: Pg_BLEND_SRC_0 | Pg_BLEND_DST_S and only while drawing lines (some 
diagonal lines only, not vertical, not horizontal).

Graphics context has all default values before the following code:

            /* Set light gray fill color */
            PgSetFillColor(PgRGB(160, 160, 160));

           /* Draw the box */
            PgDrawIRect(0, 0, 500, 500, Pg_DRAW_FILL);

            /* Set white line color */
            PgSetStrokeColor(PgRGB(255, 255, 255));

           /* Set and enable alpha blending */
           PgSetAlpha(Pg_BLEND_SRC_0 | Pg_BLEND_DST_S, NULL, NULL, 0, 0);
           PgAlphaOn();

           /* Draw the line over gray box */
           PgDrawILine(242, 47, 237, 452);

           /* Flush */
           PgFlush();
           PgWaitHWIdle();

This piece of code must draw completely invisible line over gray filled box to the current draw context. In 15/16 bpp 
video modes all works fine, but in 32 bpp io-graphics is terminated with segmentation fault error.