Asset Server issue - function hex2guid(character) does not exist

Hello Unity'ers.

I've previously installed the Asset Server on windows machines with no problems. However, now we are trying to get it running on Linux. The install appeared to go well but when we connect to the asset server from the Unity Editor we get this error:

Code (csharp):

1. ERROR:  function hex2guid(character) does not exist
2. LINE 13:     and guid = hex2guid($1[_i]);
3.                         ^
4. HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
5. QUERY:  
6.  
7.     -- update actions
8.     prepare maint_update_get_streams(integer, text[])
9.         as select maint_update_get_streams as lobj from maint_update_get_streams($1, $2);
10.     prepare maint_update_get_streams_by_guids_changesets(character(32)[],integer[])
11.         as select _i-1 as index,tag,lobj from stream, assetcontents ac, assetversion av, changesetcontents cc, asset, generate_series(array_lower($2, 1) , array_upper($2, 1)) as _i
12.             where stream = lobj
13.                 and ac.assetversion = av.serial
14.                 and cc.changeset = $2[_i]
15.                 and cc.assetversion = av.serial
16.                 and av.asset = asset.serial
17.                 and guid = hex2guid($1[_i]);
18.  

Does this look familiar to anyone? Any ideas as to what might be wrong?

Thanks!
Chris