FATAL: Failed to fork() for ftpget.

hello,

I need some help for this problem:

00:15 starts the rotation of the logfiles:

then it happens....

96/12/19 00:15:29| 118784 lines written so far.
96/12/19 00:15:29| Finished. Wrote 121256 lines.
96/12/19 00:15:29| Took 21 seconds (5774.1 lines/sec).
96/12/19 00:15:29| storeRotateLog: Rotating.
96/12/19 00:15:29| stat_rotate_log: Rotating
96/12/19 00:15:29| ftpInitialize: fork: (12) Not enough space
FATAL: Failed to fork() for ftpget.
Squid Cache (Version 1.1.0): Terminated abnormally.
CPU Usage: user 6022 sys 8660
Memory Usage: rss 0 KB
Page faults with physical i/o: 644153

and today:
96/12/20 00:15:24| 147456 lines written so far.
96/12/20 00:15:24| 151552 lines written so far.
96/12/20 00:15:24| Finished. Wrote 153955 lines.
96/12/20 00:15:24| Took 18 seconds (8553.1 lines/sec).
96/12/20 00:15:24| storeRotateLog: Rotating.
96/12/20 00:15:24| stat_rotate_log: Rotating
96/12/20 00:15:24| ftpInitialize: fork: (12) Not enough space
FATAL: Failed to fork() for ftpget.
Squid Cache (Version 1.1.0): Terminated abnormally.
CPU Usage: user 2201 sys 3108
Memory Usage: rss 0 KB
Page faults with physical i/o: 438111

we use Squid.1.1, cache-size 6144 MB,
cache_mem 16

all other default.

Who can help me !?

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