this is on devel 0_39, checked out today, and a recent (i believe yesterday) flext checkout, all compiled today.
If related somehow, the libc6 is 2.3.5-7, from unstable, the testing 2.3.5-6 had the same problem, while i didn't have this issue with 2.3.2.ds1-22 (_if_ it's related - if this will continue i guess i'll try to downgrade to see if it disappears).
a quick solution would be to define FLEXT_NOGLOBALNEW when compiling your flext externals.
cheers ... tim