If I create a password protected .odg and then create a new presentation and use
file->insert and select the password protected .odg and continually press ok it
will crash with 

    SfxFilterMatcher::GuessFilterControlDefaultUI(SfxMedium&, SfxFilter const**,
unsigned long, unsigned long, unsigned char) const
    /usr/src/debug/OOG680_m6/sfx2/source/bastyp/fltfnc.cxx:549
/usr/lib/openoffice.org/program/libsfx680li.so : 0x240730
    SfxFilterMatcher::GuessFilter(SfxMedium&, SfxFilter const**, unsigned long,
unsigned long) const
    /usr/src/debug/OOG680_m6/sfx2/source/bastyp/fltfnc.cxx:530
/usr/lib/openoffice.org/program/libsd680li.so : 0x192ADB
    SdDrawDocument::OpenBookmarkDoc(SfxMedium&)
    /usr/src/debug/OOG680_m6/sd/source/core/drawdoc3.cxx:156
/usr/lib/openoffice.org/program/libsd680li.so : 0x16B4D0
    SdPageObjsTLB::GetBookmarkDoc(SfxMedium*)

When happens is the the first time we attempt to get the bookmarks in
SdPageObjsTLB::GetBookmarkDoc we use 
mpBookmarkDoc = ((SdDrawDocument*) mpDoc)->OpenBookmarkDoc(*mpMedium);
if this fails the underlying mpDoc has closed the mpMedium on us and it is now
invalid. If we attempt to use it again on the next cycle then we crash.

So something like the following patch looks indicated, or an additional
reference taken by the dialog to ensure it remains open.