Thanks for filing, Pellesimon. I confirm the problem in 4.4.5.2 and 5.0.1.2 and in 4.3.7.2 and in 4.2.6.2 ... anyway, OK in 4.0.6.2

on 32 Bits Linux

OK in 410beta 1 - wild guess: set version to 4.2 release

The unsaved border types are fine_dashed, dashed_dot, dashed_dot_dot and double_thin.

(In reply to Oliver Specht from comment #3)
> The unsaved border types are fine_dashed, dashed_dot, dashed_dot_dot and
> double_thin.

The problems with the dashed lines are for me reproducible also with LO 5.0.1.2, Win 8.1.

For at least one of the border styles (I presume "fine dashed"), I can't find a commit in which it has worked since it was first enabled below.
Adding Cc: to vmiklos@collabora.co.uk; Could you possibly take a look at this one? Thanks
(Can't see a BZ account to Cc: Eilidh McAdam)

commit 4c3d2dcdadbcb8f2ffc2caab07d50a286341df96
Author: Miklos Vajna <vmiklos@suse.cz>
Date:   Sun Jun 16 17:47:50 2013 +0200

    Add UI for fine dashed border type
    
    Commit 7d632ff29e601c2e680c4a689997fbf552592a4b added document model /
    layout support for this, but UI was lacking.
    
    First, add a new item to the list box in
    SvxBorderTabPage::FillLineListBox_Impl().  Second, handle MAP_TWIP unit
    in svtools::GetDashing() for STYLE_FINE_DASHED. Pick up some values that
    give visually the fine dashed result when painted. (The original values
    from 2f0d406911f9790a434e46bc82ea36bb8ae714e7 in other cases seem to be
    a bit consistent already anyway.)
    
    Change-Id: Ibf1ed235d51515b065d23a6a5d5eef433162899f


The commit referenced in the above is this one:

commit 7d632ff29e601c2e680c4a689997fbf552592a4b
Author: Eilidh McAdam <eilidh@lanedo.com>
Date:   Thu Nov 15 00:29:58 2012 +0000

    Support added for fine dashing on table borders.
    
    When reading in docx documents, fine dashing provides a better visual
    match for some border types.
    Added in this patch:
     - FINE_DASHED in BorderLineStyle UNO enum and in internals
     - Import of docx table borders using this border style
    
    Change-Id: I39cfa18c915ec94d8e4ecfc6a2ca637076d1e468
    Reviewed-on: https://gerrit.libreoffice.org/1123
    Reviewed-by: Fridrich Strba <fridrich@documentfoundation.org>
    Tested-by: Fridrich Strba <fridrich@documentfoundation.org>

I'm marking this as a non-regression then, this never worked I'm afraid. I assume Eilidh added support for this for OOXML in a rush, and forgot about the strict requirement that all new features must be also implemented in the ODF filter, too.

We have a tag for this case too - adding "Whiteboard: implementationError"

Created attachment 118691 [details]
file with table with dashed borders, from LibreOffice 4.0.6.2

(In reply to Miklos Vajna from comment #6)
> I'm marking this as a non-regression then, this never worked I'm afraid.

As I wrote in comment #1: when created in 4.0.6, it was saved. See the attached file.

The attached document contains a dashed border but not a _fine_dashed_ border

<style:style style:name="Table1.A1" style:family="table-cell">

<style:table-cell-properties fo:border-bottom="0.05pt dashed #000000" fo:border-top="0.05pt dashed #000000" fo:border-right="none" fo:border-left="0.05pt dashed #000000" fo:padding="0.097cm"/>

</style:style>

(In reply to Oliver Specht from comment #9)
> The attached document contains a dashed border but not a _fine_dashed_ border

Right ... apologies.

Oliver Specht committed a patch related to this issue.
It has been pushed to "master":

http://cgit.freedesktop.org/libreoffice/core/commit/?id=ac84e4ff6135d51461122e0e1b5b39614b3e6eca

tdf#94011: load&save more border types

It will be available in 5.1.0.

The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
http://wiki.documentfoundation.org/Testing_Daily_Builds
Affected users are encouraged to test the fix and report feedback.