[gentoo-user] Downgrading glibc prevented by emerge/portage...but why initiated?

Hi,

got a problem this morning:

>>> Verifying ebuild manifests
>>> Running pre-merge checks for sys-libs/glibc-2.24-r4
 * Sanity check to keep you from breaking your system:
 *  Downgrading glibc is not supported and a sure way to destruction
 * ERROR: sys-libs/glibc-2.24-r4::gentoo failed (pretend phase):
 *   aborting to save your system
 * 
 * Call stack:
 *                ebuild.sh, line 115:  Called pkg_pretend
 *                ebuild.sh, line 348:  Called toolchain-glibc_pkg_pretend
 *   toolchain-glibc.eclass, line 507:  Called die
 * The specific snippet of code:
 *   			die "aborting to save your system"
 * 
 * If you need support, post the output of `emerge --info '=sys-libs/glibc-2.24-r4::gentoo'`,
 * the complete build log and the output of `emerge -pqv '=sys-libs/glibc-2.24-r4::gentoo'`.
 * The complete build log is located at '/var/tmp/portage/sys-libs/glibc-2.24-r4/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/sys-libs/glibc-2.24-r4/temp/die.env'.
 * Working directory: '/var/tmp/portage/sys-libs/glibc-2.24-r4/homedir'
 * S: '/var/tmp/portage/sys-libs/glibc-2.24-r4/work/glibc-2.24'
>>> Running pre-merge checks for media-sound/pulseaudio-11.0
 * Determining the location of the kernel source code
 * Found kernel source directory:
 *     /usr/src/linux
 * Found sources for kernel version:
 *     4.13.1-RT
 * Checking for suitable kernel configuration options...
 [ ok ]
 * A preallocated buffer-size of 2048 (kB) or higher is recommended for the HD-audio driver!
 * CONFIG_SND_HDA_PREALLOC_SIZE=64

I would interpret this as:

In the past emerge had updated glibc to a higher version as it want it
to install now and prevented the latter becayse it would be downgrade,
which in turn would render my box useless.

But why updateing to higher version in the first step....or attempting
to downgrade now?

And finally...ANy update is blocked for now it seems...how can I get
out of this?

Thanks a lot in advance for any help!
Cheers
Meino