[TYPO3] flexform select does not display written data

[Stano Paška]

Hi,

I have flexform select:
<firms_combo>
  <TCEforms>
    <label>LLL:EXT:kios_cosmotron/locallang_db.xml:flexform.firms_selection</label>
    <config>
      <type>select</type>
<itemsProcFunc>user_tx_kioscosmotron_userfunc->user_getFirmsCategories</itemsProcFunc>
      <size>10</size>
      <maxitems>100</maxitems>
     </config>
  </TCEforms>
</firms_combo>

Everything is ok, items in "items" part are displayed, I can select
some into the "selected" part. When I save form, selected items are
saved into tt_content.
<field index="firms_combo">
  <value index="vDEF">44,28,104</value>
</field>

But when I edit this record again, no items are displayed in the
"selected" part.

Where can be problem?

Thanks.

Stano Paška.