Mold in storage

In general, slimy brine is indicative of a fermentation problem. Your brine might be too weak (what concentration did you use?), it may be too warm, your brine might not cover the vegetables, there might be some air bubbles trapped in your ferment.

This article suggests that in the early days of sauerkraut fermentation, the concentration of slime forming bacteria - Leuconostoc - is relatively high and towards the end of fermentation it's too small to measure. It doesn't say anything about slimy brine, but it's possible that the brine is temporarily slimy in the early days of fermentation and as the acidity increases it dissipates. I've never checked a ferment this early, so I can't comment on it.

Personally, I would let it continue to ferment for a week or two and then see whether the perceived sliminess has dissipated or increased. It's possible that it's too early to tell. Slimy vegetables, without a doubt, should be discarded.

References

• http://www.culturesforhealth.com/fermented-vegetables-troubleshooting-guide

Per NC State's Extension's article on pickles and sauerkraut (some emphasis added):

Pickles or sauerkraut mold during fermentation.

Answer:

Unsafe—microorganisms are growing improperly.

Possible reasons

• Fermentation temperature was above 75°F.
• Too much salt was used, not allowing adequate lactic acid production.
• The cloth on top of the kraut was not kept clean during fermentation (may need to be replaced after skimming).

Per Penn State Extension's Saurkraut Guide (emphasis added):

Do not taste it if you see mold on the surface, feel a slimy texture, or smell a bad odor.

Their PDF on Saurkraut says:

To avoid surface mold growth, keep the cabbage submerged at all times by covering it with a plate just small enough to ft inside the fermentation container or with two or three clean quart jars filled with water. An acceptable alternative is to fill a large, sealed, food-grade plastic bag containing 4½ tablespoons of salt and 3 quarts of water.

Again, no indication of acceptable types of mold.

I cannot endorse the existing answers which indicate that mold is an acceptable part of the saurkraut making process, unless credible science based evidence is presented, from reputable sources such as University Extension Centers or, better yet, peer reviewed journal sources.