After that, I restored xchange viewer. In that moment, xchange viewer crashed.
Idea: Some kind of memory problem in xchange viewer. Perhaps xchange viewer removes data from memory if it's idle for a longer time and than it has trouble with restoring.
PDFXCview.exe 2.0.0040.0004 caused exception C0000006 at address 008FA8DA (Base: 400000)
EAX=01566084 EBX=00000100 ECX=00000040 EDX=00000000 ESI=01565F84
EDI=017B00B8 EBP=022FF0BC ESP=022FF0B4 EIP=008FA8DA FLAGS=00000212
CS=001B DS=0023 SS=0023 ES=0023 FS=003B GS=0000
3FFBCCCCCCCCCCCCD000 00000000000000000000 EE18068293A8040A5000
F5F80319F72401CC6F60 0608019500000407C558 78847C92056D00150608
0ECA013CFD4C00000000 01F80000000000000000 SW=0000 CW=027F