I/O error when make swap directory

[David,Lan Bin]

I run squid -z and get the following error:

1999/02/27 14:17:07| Creating Swap Directories
FATAL: Failed to make swap directory /home/grad/lanbin/sqid/cache/02/88: (5) I/O error
Squid Cache (Version 2.2.DEVEL3): Terminated abnormally.
CPU Usage: 0.310 seconds
Maximum Resident Size: 0 KB
Page faults with physical i/o: 22

Any tips?
tia.

lb