Forum OpenACS Development: User tracking bug

I've installed User Tracking and got it to present statistics etc. however, when I click "update data" I get the following error message:

The file is /user-tracking/loading2

(I'm running OpenACS 5.2.3 on Postgres 7.4)

Error:
expected integer but got "08" (looks like invalid octal number)
while executing
"expr $lastday + 1"
invoked from within
"if {[exists_and_not_null LastTime]} {

set campos [split $LastTime "/-"]

set lastyear [lindex $campos 2]
set lastmonth [linde..."
("uplevel" body line 42)
invoked from within
"uplevel {
ad_page_contract {
@author sergiog (mailto:sergiog@tid.es)
@author doa (mailto:doa@tid.es)
@creation-date 2005-01-10
} -query {
{config ""}
..."
(procedure "code::tcl::/var/lib/aolserver/nccedudotlrn/packages/user-tra..." line 2)
invoked from within
"code::tcl::$__adp_stub"
invoked from within
"if { [file exists $__adp_stub.tcl] } {

# ensure that data source preparation procedure exists and is up-to-date
adp_init tcl $__adp_stub
..."
("uplevel" body line 3)
invoked from within
"uplevel {

if { [file exists $__adp_stub.tcl] } {

# ensure that data source preparation procedure exists and is up-to-date
adp_init t..."
(procedure "adp_prepare" line 2)
invoked from within
"adp_prepare "
(procedure "template::adp_parse" line 30)
invoked from within
"template::adp_parse [file root [ad_conn file]] {}"
(procedure "adp_parse_ad_conn_file" line 5)
invoked from within
"$handler"
("uplevel" body line 2)
invoked from within
"uplevel $code"
invoked from within
"ad_try {
$handler
} ad_script_abort val {
# do nothing
}"
invoked from within
"rp_serve_concrete_file [ad_conn file]"
(procedure "rp_serve_abstract_file" line 60)
invoked from within
"rp_serve_abstract_file "$root/$path""
("uplevel" body line 2)
invoked from within
"uplevel $code"
invoked from within
"ad_try {
rp_serve_abstract_file "$root/$path"
set tcl_url2file([ad_conn url]) [ad_conn file]
set tcl_url2path_info..."