Hello,
this is my command line for lazarus
make LCL_PLATFORM=qt CPU_TARGET=x86_64 OS_TARGET=win64 OPT="-dUSE_QT_45 -g -gl"

win 8 x64
fpc svn lazarus svn r49771
qt-4.8.6-x64-mingw482r3-seh
Qt4Pas5.dll is 64bit

IDE building, when Start IDE on splash screen, create error "access violation" message 3 time, then application close. this is bt results

f:\opt\lazarus>f:\opt\lazarus\mingw64\bin\gdb lazarus GNU gdb (GDB) 7.1.90.20100730-cvs
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-w64-mingw32".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from f:\opt\lazarus/lazarus.exe...done. (gdb) run
Starting program: f:\opt\lazarus/lazarus.exe
[New Thread 1176.0xde4]
warning: SHIMVIEW: ShimInfo(Complete)

warning: FTH: (1176): *** Fault tolerant heap shim applied to current process. T
his is usually due to previous crashes. ***

[New Thread 1176.0xfdc]

Program received signal SIGSEGV, Segmentation fault. 0x00000000651079d5 in QAction::shortcut() const () from f:\opt\lazarus\QtGui4.dll