Ubuntu :: U9.10 Every Second Boot Fails, Does Not Mount?

i am very frustrated with my ubuntu system which is meant as a workstation-server. It seems to loose track of its drives every time I add diskspace.Now every other boot (it seems) it says (among other things: VFS: can't find ext3 filesystem on dev sdd5) drops me to a maintenance-shell and asks for the root password (whats that in ubuntu, the user password does not word) - so I can't log in. Ctrl-D sometimes works and it boots through or boots after warmstart by Ctrl-Alt-Del.

[edit: found out that with alt-f3 i can access a normal shell - good - but how do I start up the GUI in ubuntu? - startx does not work] I have manually fsck'd all ext2/3 partitions form a ubuntu booted from CD - still it says something about not being able to mount /dev/sdd5.Since every now and then I have so much trouble bringing up the machine I am quite unhappy. I suspect the constant updates are prone to break things - is that so?And how do I resolve this issue. Unfortunately there is nothing about the errors in /var/log/messages or dmesg so it is no use posting it here. Where are such errors recorded? [edit: I changed the mappings in fstab to resolve the issue - still it is awkward that drives get messed up so easily. Are UUIDs in fstab less error prone when moving drives around, or do they have other issues?]