We are on AIX.
I had theis issue today.
And surprisingly, I got the following error when I tried loading a zero byte file.
But when I ran the same command with a file having data, it loaded fine

arsload: Processing file >/cna1/cfsc/SystemLogMixed/11796736_systemLogMixedIND_132-23-2345-23-45-65<
arsload: Load Version <8.5.0.5> Operating System <AIX> <6.1>
arsload: Server Version <8.5.0.5> Operating System <AIX> <6.1> Database <DB2> <09.07.0005>
arsload: 12/13/12 07:15:59 -- Loading started, --UNKNOWN-- bytes to process
Unable to allocate enough memory. File=arslacif.c, Line=1767
Loaded 0 rows into the database
arsload: 12/13/12 07:16:04 Loading failed
arsload: Processing failed for file >/cna1/cfsc/SystemLogMixed/11796736_systemLogMixedIND_132-23-2345-23-45-65<
arsload: Processing has stopped. The remaining files will NOT be processed.
Cheers
Pankaj.