We believe that your issue has been closed by the upload of
Version 0.3.36 of grml-rebuildfstab from Michael Prokop <mika@grml.org>.
The explanation is attached below

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Format: 1.8
Date: Fri, 13 Nov 2009 17:21:16 +0100
Source: grml-rebuildfstab
Binary: grml-rebuildfstab
Architecture: source all
Version: 0.3.36
Distribution: unstable
Urgency: low
Maintainer: Michael Prokop <mika@grml.org>
Changed-By: Michael Prokop <mika@grml.org>
Description: 
 grml-rebuildfstab - fstab-rebuilder for grml
Changes: 
 grml-rebuildfstab (0.3.36) unstable; urgency=low
 .
   * Do not execute it if something is mounted directly to /mnt.
     [Closes: issue441]
   * Bump Standards-Version to 3.8.3 (no further changes).
Checksums-Sha1: 
 d857602a9f0505622c13fe2c04d6cfd6508f0502 898 grml-rebuildfstab_0.3.36.dsc
 2ecf708c1a7ef89af99d33d83948e4e4c92526de 10560 grml-rebuildfstab_0.3.36.tar.gz
 9ebcc4223bd379a148bb43c43499d060d2764b4c 12202 grml-rebuildfstab_0.3.36_all.deb
Checksums-Sha256: 
 ec5b22c1439856e19d10cdc6fd8968365a9441d3a075f76a609d49c77c76e056 898 grml-rebuildfstab_0.3.36.dsc
 b5bcbe77ce12b828789afe7ab6cb5e48004ca1cae5b1612bbc4c985397408dd0 10560 grml-rebuildfstab_0.3.36.tar.gz
 f7441e823c166e294472077b3f41b766e27cd88e12042807e0950a0f441a2b53 12202 grml-rebuildfstab_0.3.36_all.deb
Files: 
 e5cc2dbb244926353702527117bcf9df 898 grml optional grml-rebuildfstab_0.3.36.dsc
 a18a4a6bc0feda56024354087af3975f 10560 grml optional grml-rebuildfstab_0.3.36.tar.gz
 944ea8d5ccb80d0f737998d4b3265f85 12202 grml optional grml-rebuildfstab_0.3.36_all.deb

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Thanks to Florian Heimgaertner for the suggestion:

Do not create directories/files/... in /mnt if something is mounted directly 
to /mnt.