Hi,
Many thanks for you help. Unfortunately, still I can't display. v.info shows bad region limits (see below). Could the mistake be about bad region settings while importing?
Thanks again,
Roman
import process follows
g.region n=45N s=37N w=10W e=5E
v.in.dgn - all defaults accepted
This outputs a lot of warnings about complex element header ignored, complex elements parts written
Next I run v.support - all defaults accepted
###output for v.support-topology########################
Selected information from vector header
Organization:
Map Name:
Source Date:
Orig. Scale: 0
Snapping threshold 0.00
No snapping will be done.
Reading Vector file 100%
Building areas 100%
Building islands (no islands present)
Attaching labels
Failed to attach an attribute (category 2) to a line.
Failed to attach an attribute (category 3) to a line.
Failed to attach an attribute (category 8) to a line.
Failed to attach an attribute (category 14) to a line.
Failed to attach an attribute (category 18) to a line.
Failed to attach an attribute (category 29) to a line.
WARNING: line 80 label: 32 matched another label: 34.
Failed to attach an attribute (category 45) to a line.
Failed to attach an attribute (category 51) to a line.
Failed to attach an attribute (category 52) to a line.
Failed to attach an attribute (category 55) to a line.
Failed to attach an attribute (category 56) to a line.
Number of lines: 218
Number of nodes: 215
Number of areas: 0
Number of isles: 0
Number of atts : 45
Number of unattached atts : 11
Snapped lines : 0
###########################################################
Editing category file I have found some category strings have problems with tilde (system locale is spanish), but this seems not to be related with failed attachments
#########Output from v.info#################################
+-----------------------------------------------------------
Layer: prov Date:
Mapset: PERMANENT Organization:
Location: GEO-ED50 Name of creator:
DataBase: /var/GRASSDATA/
Title: ( prov)
-------------------------------------------------------------
Type of Map: Vector (level: 2) Number of Categories: 56
Number of lines: 218 Number of areas: 0
Number of islands: 0
Projection: Latitude-Longitude (zone 0)
N:0 S:0
E:0 W:0
Source date:
Original scale 1:0 Map threshold: 0.00000 Comments:
##############################################################
As you can see, region limits are somewhat shocking
g.region vect=prov
##########g.region -p output##################################
projection: 3 (Latitude-Longitude)
zone: 0
datum: eur50
ellipsoid: international
north: 0:00:03N
south: 0:00:03S
west: 0:00:03W
east: 0:00:03E
nsres: 0:00:03
ewres: 0:00:03
rows: 2
cols: 2
##############################################################
funny, it isn't? 
After this, d.vect still shows nothing
Running v.llabel doesn't help
I have not run v.alabel since v.info says there are no areas.
Best regards,
Roman