When dragging cards in various games, aisleriot 2.15.5 crashes. I've had it happen in Backbone, Ten Across, Isabel, Seahaven and others. This is Gnome 2.15.90, Gentoo AMD64.

Memory status: size: 204795904 vsize: 204795904 resident: 30044160 share: 10756096 rss: 30044160 rss_rlim: -1
CPU usage: start_time: 1154063538 rtime: 1223 utime: 1131 stime: 92 cutime:0 cstime: 0 timeout: 0 it_real_value: 0 frequency: 100

Variation: Backbone
Seed: 3169096429
Scheme error:
	(car Wrong type argument in position ~A: ~S (1 #<freed cell 0x2b84c136dc40; GC missed a reference>) #f)
Scheme tag:
	wrong-type-arg

Backtrace:
In unknown file:
   ?: 0* [is-legal-move? 24 #<freed cell 0x2b84c136dc40; GC missed a reference> 13]
In /usr/share/sol-games/backbone.scm:
 149: 1* (and (not (= start-slot end-slot)) (not (eq? card-list (quote ()))) ...)
 152: 2  (or (and # #) (and # #))
   ...
 163: 3  (and (= (get-suit #) (get-suit #)) (= (get-value #) (- # 1)))
 164: 4* [= ...
 164: 5*  [get-suit ...
 164: 6*   [car #<freed cell 0x2b84c136dc40; GC missed a reference>]


Deck State:
	Slot 0
		(3 12 #f), (3 11 #f)
	Slot 1
		(3 5 #f)
	Slot 2
		(2 1 #f), (2 2 #f), (2 3 #f), (2 4 #f), (2 5 #f)
		(2 6 #f), (2 7 #f)
	Slot 3
		(3 1 #f), (3 2 #f), (3 3 #f), (3 4 #f), (3 5 #f)
		(3 6 #f), (3 7 #f), (3 8 #f), (3 9 #f)
	Slot 4
		(3 1 #f)
	Slot 5
		(0 1 #f), (0 2 #f), (0 3 #f), (0 4 #f), (0 5 #f)
		(0 6 #f), (0 7 #f), (0 8 #f), (0 9 #f), (0 10 #f)
		(0 11 #f), (0 12 #f), (0 13 #f)
	Slot 6
		(1 12 #f)
	Slot 7
		(Empty)
	Slot 8
		(0 1 #f), (0 2 #f), (0 3 #f), (0 4 #f)
	Slot 9
		(1 1 #f), (1 2 #f), (1 3 #f), (1 4 #f), (1 5 #f)
		(1 6 #f), (1 7 #f), (1 8 #f), (1 9 #f), (1 10 #f)
	Slot 10
		(1 1 #f)
	Slot 11
		(Empty)
	Slot 12
		(0 8 #f), (0 7 #f), (0 6 #f)
	Slot 13
		(2 13 #f)
	Slot 14
		(1 8 #t), (3 13 #t), (1 7 #t), (1 9 #t), (1 11 #t)
		(3 11 #t), (3 13 #t), (0 9 #t), (3 4 #t), (1 11 #t)
		(2 8 #t), (0 5 #t), (1 12 #t), (3 6 #t), (3 9 #t)
		(1 5 #t), (3 12 #t), (3 10 #t), (0 11 #t), (0 10 #t)
		(2 12 #t), (0 12 #t)
	Slot 15
		(2 9 #f), (2 9 #f), (3 8 #f), (2 5 #f), (1 4 #f)
		(1 6 #f), (2 8 #f), (2 10 #f), (1 13 #f), (1 10 #f)
	Slot 16
		(2 3 #f), (2 2 #f)
	Slot 17
		(2 13 #f), (2 12 #f), (2 11 #f), (2 10 #f)
	Slot 18
		(1 3 #f)
	Slot 19
		(1 2 #f)
	Slot 20
		(3 3 #f)
	Slot 21
		(2 4 #f)
	Slot 22
		(2 6 #f)
	Slot 23
		(3 10 #f)
	Slot 24
		(Empty)
	Slot 25
		(Empty)
	Slot 26
		(Empty)
	Slot 27
		(0 13 #f)
	Slot 28
		(1 13 #f)
	Slot 29
		(3 2 #f)
	Slot 30
		(3 7 #f)
	Slot 31
		(2 1 #f)
	Slot 32
		(2 7 #f)
	Slot 33
		(Empty)
	Slot 34
		(Empty)
	Slot 35
		(Empty)
	Slot 36
		(Empty)
Backtrace was generated from '/usr/libexec/aisleriot'

Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread 47849081218368 (LWP 8050)]
0x00002b84bb104da5 in __libc_waitpid (pid=8232, stat_loc=0x7ffff562dffc, options=0) at ../sysdeps/unix/sysv/linux/waitpid.c:32
	in ../sysdeps/unix/sysv/linux/waitpid.c

+ Trace 69723