enable and disable keys

Hi All,
We are doing load data into a table using LAD DATA INFILE process. Below is
the method we are following.

1. create empty table with all the indexes.
2. disable keys
3. Load data using LAD DATA INFILE, close to 99 Million records which takes
around 3 hrs
4 . Enable keys

Table size is around 19.5 gb

There is one primary key, 2 non unique indexes and one FULLTEXT INDEX.

Enable kyes goes fine for couple of hrs with "REPAIR BY TMP", but then
switches to "REPAIR BY KEYCACHE" and writes a log in the error log
file "Warning:
Enabling keys got errno 28, retrying"

What could be the problem.

System has 8 cpu and 16GB RAM

I have set myisam_max_sort_file_size=98GB
myisam_sort_buffer_size=750MB.

/tmp folder has 16GB free space.

please let me know, this problem is causing lot of dealy for other process
to run.

regards
anandkl