I must say i have no idea from linux development... but i know under amd64 linux are 2 lib folders.
drwxr-xr-x 35 root root 16384 2011-01-09 15:39 lib
lrwxrwxrwx 1 root root 24 2010-08-31 21:05 lib32 -> /emul/ia32-linux/usr/lib
lrwxrwxrwx 1 root root 3 2010-08-31 21:05 lib64 -> lib
The gamserver uses the /usr/lib32 folder which is linked to /emul/ia32-linux/usr/lib - it run's over the ia32-libs they are emulate an 32bit system under amd64 - the problem ist for amd64 doesn't exists ia32-lib package which contains gnutls. Your Link's doesn't help because:
http://packages.debian.org/lenny/amd64/libcurl3-gnutls/download -> this installs the lib to /usr/lib64/ and cant be used for an 32bit software
http://packages.debian.org/lenny/i386/libcurl3-gnutls/download -> this can't be installed on an amd64 installation.
Under the /usr/lib && /usr/lib64 is gntuls available - but the gameserver do not use this folder because your mod is only 32bit
I think i must install 1 server with i386 .... or our customers are unhappy
PS: @killermonkey: nice profil pic
Best regards from austria,
Alexander