Slime in Fermented Pickle brine
On its page, White Film On Cultured Vegetables, Cultures for Health identifies kahm yeast as the probable culprit. Many reference sites indicate that the food is safe to eat as long as mold is not present. The yeast film should be removed as it may affect the flavor of the food and it may adversely affect digestion.
Kahm yeast formation can occur because:

The batch is insufficiently acidic
There is not enough salt in the brine
The culturing temperature is too warm
The batch is over-exposed to oxygen
Good hygiene was not observed during preparation

You should be able to avoid kahm yeast formation in the future by following good lacto-fermentation procedures.