It happened with bob09 and ndisles. I'll experiment again tonight with other terrains.
I did notice, however, that for ndisles I did not have any tables listed as available to upload (offline or online) even though I had files in the chconfig folder for ndisles. I noticed that the ndisles tables and the dotisles (my custom tables) in the folder had the exact same timestamps.
When I deleted the ndisles tables and went to create an arena, it dumped me as usual, but upon re-entering I now had my custom "dotisles" tables listed and was able to upload them. When I checked the chconfig folder later, I again had ndisles tables along with my custom tables, but this time the timestamps were different and I could still see them to select them for upload.
When I loaded bob09, I was always able see tables to choose from; the timestamps for the bob09 and the dotbob tables were different. Something weird must have happened with ndisles for the table sets to have the same timestamp.