Check out your log files :

- dmesg
- /var/log/messages

There you should find what went wrong

Thanks, this is what I found:
Which actually sounds quite logical to me if the mounting proces from fstab starts before I login, because if that's the case, then there is no user-homedirectory (so no ~). Do you know if the mounting proces from fstab start before or after loging in. To me it seems that is done before loging in. If that is the case, then there is no way to automaticaly mount the share to the homedir of the user that logs in using fstab.

The ~ refers to the home of the user currently used so it points to /root/jdhd (services are started with root user) but not finding the directory

try using the full path of your home directory (/home/'username'/jdhd) instead of the ~

I fixed it! By doing a little debugging I reached the same conclusion as the above post. The system was looking for /root/jdhd and offcourse didn't find this. Besides that there was another error in the fstab, I didn't need to include "auto" in the line, because al the lines in fstab are mounted automatically except for the lines which contain "noauto". Here is the working fstab line:
I now want to modify it all so that the jdhd-share only get's mounted when the user "jethro" logs in. So I figure I have to put something like 'mount -t smbfs //ephyra.jesdesign.nl/jdhd ~/jdhd' in .bashrc or something. The problem is that I'm not allowd to run the 'mount -t' command unless I'm root. Is there a way out of this? Besides that I have to figure out a way to pass the username and password using the mount command.

I think you need NFS for that but i'm not sure ... I'll have to look in to that

I don't believe you'd need or want to tell mount the filesystem type anyhow, because it will (by default) check the mount location against fstab. This means that typing "mount //servername/sharename" will automatically mount it with the FS type and mount location found in fstab (in this case smbfs and ~/jdhd, respectively). Passing it information contrary to what's in fstab will tell it to ignore the fstab defaults, thereby making you lose any settings inside it; the important one here being the "user" string, allowing any user with credentials to mount this location.

But I think .bashrc can't run the "mount" command for the user "Jethro" because it's not root. How can I fix that?

Log onto that user and type mount. If you get anything other than command not found, it should work.
If you do get a command not found, just change the permissions on /bin/mount to allow execution for your user, or make a sudo entry.