Maximizing same application makes X stop refreshing and receiving keyboard and mouse events.
Backtrace shows that libdrm seems to be stuck trying to get som kind of lock.

Here the backtrace:
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb7623049 in ioctl () from /lib/libc.so.6
#2  0xb72cdf44 in drmGetLock (fd=7, context=4294966784, flags=3216499876) at xf86drm.c:1231
#3  0xb6f5f6c1 in r200GetLock (rmesa=0x80b9e78, flags=0) at r200_lock.c:77
#4  0xb6f5e2e4 in r200Clear (ctx=0x80c2e10, mask=512, all=1 '\001', cx=<value optimized out>, cy=<value optimized out>, cw=300, ch=300) at r200_ioctl.c:623
#5  0xb709a5db in _mesa_Clear (mask=0) at main/buffers.c:178
#6  0xb76af0cb in gl_stencil_line_clear (da_w=1280, da_h=911) at drawing3d.c:2277

Here the strace:
ioctl(4, 0x40106450, 0xbf96c31c)        = 0
ioctl(4, 0xc0086451, 0xbf96c4e0)        = 0
ioctl(4, 0x40106450, 0xbf96c35c)        = 0
ioctl(4, 0x40186448, 0xbf96c4e0)        = 0
ioctl(4, 0x4004644c, 0xbf96c4ec)        = 0
write(1, "   sub axis 3 -> Valid: 1 | On s"..., 62   sub axis 3 -> Valid: 1 | On screen: 0 | Fully on screen: 0
) = 62
munmap(0xae499000, 1167360)             = 0
ioctl(4, 0x40106450, 0xbf96c31c)        = 0
ioctl(4, 0xc0086451, 0xbf96c4e0)        = 0
ioctl(4, 0x40106450, 0xbf96c35c)        = 0
ioctl(4, 0x40186448, 0xbf96c4e0)        = 0
ioctl(4, 0x4004644c, 0xbf96c4ec)        = 0
ioctl(4, 0x4004644c, 0xbf96c4fc)        = 0
mmap2(NULL, 1167360, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xae499000
write(1, "[find_axis_to_plot] Axis type: 1"..., 33[find_axis_to_plot] Axis type: 1
) = 33
write(1, "[intersect 3d segment with scree"..., 107[intersect 3d segment with screen] (0,000000, 0,000000, 0,000000) (0,000000, 7,500000, 0,000000) Points: 2
) = 107
ioctl(4, 0x40106450, 0xbf9582cc)        = 0
ioctl(4, 0x6444, 0)                     = 0
ioctl(4, 0x4008642a

Running it thru STRACE is MUCH MORE DIFFICULT to trigger the error, suggesting that somehow timing between ioctl calls (affected by strace in between) is critical to reproducing the bug. Without it, launching the app, pressing ALT+F10 makes it instantly to block X.

Program versions:
xorg-server 1.1.1
mesa 6.5 (with some distro applied patches)
glib 2.10.3
gtk+ 2.8.20
cairo 1.2.0
kernel 2.6.17 (with gentoo added patches)
Distro: Gentoo
This backtrace hardware:
VT8377 northbridge, Radeon RV280 chip