Forum OpenACS Development: Problem installing file storage

I'm running:

freebsd    4.7 stable
postgresql 7.1
aolserver  3.4.2
pgdriver  2.0
OACS  4.5

(hosted with hub.org)

I've got the site up, and got other packages running (e.g., bboard)

When I install file storage and click on the application link from the site map, I get

---------------
Request Error
syntax error in expression " - "
    while executing
"expr $folder_id - [fs_get_root_folder]"
    invoked from within
"set nonroot_folder_p [expr $folder_id - [fs_get_root_folder]]"
    ("uplevel" body line 29)
    invoked from within
"uplevel {
          ad_page_contract {
    Front page for file-storage.  Lists subfolders and file in the
    folder specified (top level if none is spe..."
    (procedure "code::tcl::/usr/local/www/octavianworld.org/openacs-4/packag..." line 2)
    invoked from within
"code::tcl::$__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 3)
    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 7)
    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([ad_conn url]) [ad_conn path_inf..."

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any suggestions? I got file storage running just fine on an earlier site I put up using OACS 4-5b1, running on the same stack...

Many Thanks!