about auctex in Debian 6 , I can not preview math formula
 

I use emacs 23.2.1 and auctex 11.85-1 in Debian 6 .
When I preview ' ${a_n }$ ' , this simple formula , I get the following errors :



gs -dOutputFile=(_region_.prv/tmp5813419/pr1-1.png) -q -dSAFER
-dNOPAUSE -DNOPLATFONTS -dPrinted -dTextAlphaBits=4
-dGraphicsAlphaBits=4 -sDEVICE=png16m -r155.52x155.384
GS>{DELAYSAFER{.setsafe}if}stopped pop/.preview-BP currentpagedevice/BeginPage get dup null eq{pop{pop}bind}if def<</BeginPage{currentpagedevice/PageSize
get dup 0 get 1 ne exch 1 get 1 ne or{.preview-BP 0.184314 0.309804
0.309804 setrgbcolor clippath fill 0.980392 0.921569 0.843137
setrgbcolor}{pop}ifelse}bind/PageSize[1 1]>>setpagedevice/preview-do{[count 3 roll save]3 1 roll dup length 0 eq{pop}{setpagedevice}{ifelse .runandhide}stopped{handleerror quit}if aload pop restore}bind def [(_region_.prv/tmp5813419/preview.ps)(r)file]aload
exch dup 0 setfileposition 21394()/SubFileDecode filter cvx .runandhide
aload pop dup dup 21394 setfileposition 137()/SubFileDecode filter
cvx<<>>preview-do

Error: /invalidfileaccess in --file--
Operand stack:
** --nostringval--** (_region_.prv/tmp5813419/preview.ps)** (r)
Execution stack:
**
%interp_exit** .runexec2** --nostringval--** --nostringval--**
--nostringval--** 2** %stopped_push** --nostringval--**
--nostringval--** %loop_continue** --nostringval--** --nostringval--**
false** 1** %stopped_push** .runexec2** --nostringval--**
--nostringval--** --nostringval--** 2** %stopped_push** --nostringval--

Dictionary stack:
** --dict:1160/1684(ro)(G)--** --dict:0/20(G)--** --dict:72/200(L)--
Current allocation mode is local
Last OS error: 2
Current file position is 532
GS<3>

What is the matter ?


Thanks first of all !