How much gelatin are you using and is it in addition to Irish moss or some other fining material in the boil?
I use small packets of Knox unflavored gelatin which can be purchased in 4 pack for $1 at Walmart. I use one packet if I'm doing one keg at a time, but 1/2 packet in 5 gallons will do the trick.
Here is my process for adding gelatin:
Overnight or for 24 hours I'll chill the beer below 50 degrees. I try to get it as close to 35 as I can. After the beer is chilled, prepare the gelatin:
1) Fill a pyrex or other microwave safe container with 6-8 oz of water
2) Boil the water (on our microwave which is 1200 watts, I set it for 8 minutes, it starts boiling within the first 3 minutes)
3) With a piece of foil, sprayed with star san ready, open the microwave door and quickly cover the pyrex.
4) Sanitize a thermometer with Star San and stick it through the foil into the water. The thermometer is a nice tool to stir with and take the temperature as well.
5) When the temp of the water falls below 190 pour in half a packet of Knox unflavored gelatin and stir the thermometer. Above 190, you'll actually make gelatin and get some nice chunkies in your final beer
6) Leave the solution for 5-10 minutes to let the gelatin "hydrate."
7) Pitch the solution into the beer while it's still above 110F, then mix in gently.
After 24 hours you'll see a huge difference. I usually shoot for 2-3 days. My drop hop schedule is usually 68-70 degrees days 1-6. Day 7 chilling the beer and days 8-10 gelatin.