trasparent texts during editing.

Hello from Italy everybody.
I use Autocad 2004 eng full.
Sorry for my unprecise english.
During editing multiline texts sometimes Autocad shows the lines slightly
trasparently.
If you want you can have a look here:
\autocad.jpg
It occurs on different drawings with no regularity. Moreover it happens
every now and then on the same multiline text.
It is very disturbing and it seems not to be a variable to set or a
videoboard arrangement.
Did anybody have the same problem?
How can I sort it out?
thanks
francesco