This is real case !

Part of debug log of vanilla 2.0.5:
18475:20130228:150325.247 Starting Zabbix Server. Zabbix 2.0.5 (revision 33558).
...
18475:20130228:150325.248 NodeID: 998
...
18481:20130228:150339.182 query [txnlev:1] [select e.expression,e.expression_type,e.exp_delimiter,e.case_sensitive from regexps r,expressions e
where r.regexpid=e.regexpid and r.name='File systems for discovery']
18481:20130228:150339.182 DBlld_process_discovery_rule() f_macro:'

' f_regexp:'@File systems for discovery'

I did a patch:

Index: src/libs/zbxdbhigh/lld.c
===================================================================
--- src/libs/zbxdbhigh/lld.c    (revision 33709)
+++ src/libs/zbxdbhigh/lld.c    (working copy)
@@ -2373,8 +2373,8 @@
                        result = DBselect("select e.expression,e.expression_type,e.exp_delimiter,e.case_sensitive"
                                        " from regexps r,expressions e"
                                        " where r.regexpid=e.regexpid"
-                                               " and r.name='%s'",
-                                       f_regexp_esc);
+                                               " and r.name='%s'" DB_NODE,
+                                       f_regexp_esc, DBnode_local("r.regexpid"));

                        zbx_free(f_regexp_esc);

It helped to get this line (as it should be, IMO):
4877:20130228:160139.625 query [txnlev:1] [select e.expression,e.expression_type,e.exp_delimiter,e.case_sensitive from regexps r,expressions e where r.regexpid=e.regexpid and r.name='File systems for discovery' and r.regexpid between 99800000000000000 and 99899999999999999]

In production environment I have this:
mysql> select * from regexps;
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
9 rows in set (0.00 sec)

As you see there two regexps with the same name - "discovery filtering on snmp devices", but they use different expressions.

And all my LLD discovery rule with the regexp name "discovery filtering on snmp devices" on master nodeid=1 do NOT work correctly - they do NOT discover experted resources.

Note - in the code I saw many places where no check for nodeid when selecting a global regexp.
So probably you need to check them all, but I'm not very sure here.