I'm just wondering why you re-potted?

Sounds like your keeping the soil too wet, and or, have over-potted, possibly poor drainage, or heavy soil. I'm not sure what you can do about the mildew other than scraping it off the top part of the soil and letting the soil in the pot dry out more and keeping the plant out off drafts. Better air circulation can help! If your misting, you'll need to stop.

Billy Rae

Cyclamen go dormant (and need to be encouraged to do so) after they bloom. Just so you know.

About the 'white stuff'. Are you talking about powdery mildew, which cyclamen are susceptible to, or something else? I'm a bit confused by your description.

Cora, Cyclamens do best in small pots, if possible, repot back to its original container. Plasic is best, second to clay.
After flowering, Cylamens go into dormancy, like Rhizo said.
When dormant, reduce watering, keep cool, and do NOT fertilize.
White stuff is probably mold. If soil is kept wet, Cyclamens are prone to mold. For the time being, wipe off mold, and if/when you repot, discard old soil, use a well-draining type medium. Cactus/Succulent soil is fine. If you keep in too large a pot, and soil remains wet, mold will continue growing. Cylmamen mites are another problem, but we'll assume your plant is overwatered.
If possible, during summer, set outdoors in a shady spot. Keep it sheltered out of rain, and like Billy Rae said, if you mist, stop. (believe me, I'm into misting plants) but fuzzy leaf plants do not get sprayed. While old leaves die, new will grow in. Remove old, brown leaves. I find, bottom-watering best for Cyclamen. Corms rot easily, so proper watering is very important. Toni
PS. When you wipe mold, add a little rubbing alcohol on paper towel or dust cloth. I've also heard Peroxide helps, but not sure, so try the alcohol.

Cora has determined that the white stuff is, indeed, powdery mildew. Powdery mildew fungus is not uncommon on cyclamen.

I used FungAway (see the link below) for powedery mildew, and it worked very well. be sure to mix according to directions, and not with a higher concentration, because the plant might not like it.

I also read somewhere that people use lysol for powdery mildew, but I haven't used that myself. From what I read, lysol might spot the leaves (which is probably not a big deal if the plant is heading for dormancy?), and it's also less efficient.

Here is a link that might be useful: FungAway

Rhizo, why do you say, Corn has determined the white stuff is powdery mildew when she hasn't yet replied? She called it white stuff/white powder. I doubt she knows what her Cyclamen has.
Whether or not it's mold or powdery mildew, it needs to be cleaned and treated. IMO, underpotting and proper watering will benefit. Until she determines what this 'white stuff' is, using a non-needed chemical may in fact harm her plant.

Cora, btw, Cyclamen are poisonous, so if you have pets or young children, keep them away. Wash hands after handling. Toni

OOps! I DID reply to an email (from Rhizo) before I got back to this site. Sorry for the vague description of the "white stuff". But you all have been super generous with your information and I'm very grateful. I've shared it all with my DIL. And I do have a puppy who has NO respect for my plants, potted or otherwise. Thanks for the heads-up. This forum is GRRRRRRRRRREAT!!! cora

Oops, is right! Cora is more informed about her plant diseases than she let on! And according to our exchanges, there is no doubt that her plant has powdery mildew. OK, Toni?

Now! Alenka! The majority of people probably aren't aware of how toxic (to humans and other animals) some fungicides can be. The active ingredient in your FungAway is one of the scary ones, to be sure. That's EXACTLY why it should never be used for house plants. When a product's label says for ornamental or lawn use (for example), you can infer that indoor or greenhouse use is not recommended.

Bayleton (triadimefon) should be handled with great caution! Please, we want you and your family to be safe and healthy.

Thanks, rhizo! I used FungAway a while ago, and somehow checking for toxicity wasn't on my mind back then -- and actually after I posted, I started wondering about its toxicity, and I was just now reading the info available online -- so thank you for the warning. I should have done my homework, especially before suggesting something to others. Thanks!