Ubuntu :: Cannot Mount Partitions Anymore - Error Mounting: Mount Exited With Exit Code 1: Helper Failed

First of all: it's been more than 12 years ago since I worked with Linux, and a lot has changed in the meantime. But I considered it a challenge to install Ubuntu 9.10 and lateron upgraded to 10.04 LTS without any troubles, until now:

Except my main partition ("/") all other partitions fail to mount. All NTFS partitions from my other OS and also 2 other linux ext4 partitions I've made are not accessible anymore. and, what bothers me the most: I deleted those 2 new linux partitions in the meantime because I couldn't access them initially because Root was the owner (Duh! root is standard disabled in Ubuntu, right?). After an attempt to try to automount all partitions following the help guides I got now big grey errors on my splashscreen while booting, telling that an error occured with e.g. /media/Backup because it is missing or it cannot be mounted, with 3 options below: waiting, skipping or using a command prompt to solve this. I always choose Skip for safety.

Now if I want to see the content of all my other partitions I got a popup telling me unable to mount e.g. /media/Downloads and the message included:

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