did you try installing the ia32 libs and chrooting the ia32 libs in x64? there is a nice tuts on how to use prop bin in 32 bit env. google up. and gnu's flash supports flash 8, where as adobe IMHO flash 7. not so sure.
gnash is ideal, if you cvs and svn or git up from the source. and not the .deb bin. if you ask _me_? i would suggest build from source and check for CV's list from vulnerability and update and apply patches as per the need of the hour.
good luck.