Dynamic SQL Error Messages!

Have this dynamic sql statement that I'm working on.  It works fine outside the execute (running the query by iteself) and prints fine but when I execute it, I get errors.  Spacing is good.  Here is the SQL statement.

 set @sql = 'insert into #participantInfo (strfirstname,strlastname,strindividualfk,strusername,dtelastlogin,blninactive,fk_intrightid,imgPhoto,
 stre_mail,strmiddleinitial,straddress1,straddress2,strcity,fk_intlocationid,strpostalcode,strhomephone,strbusinessphone,strmiscinfo1,
 strmiscinfo2,strsecretquestion,dteDateOfBirth,intgender,strsecretanswer)
 select p.strfirstname,p.strlastname,p.strindividualfk,l.strusername,l.dtelastlogin,p.blninactive,r.fk_intrightid,p.imgPhoto,
 p.stre_mail,p.strmiddleinitial,p.straddress1,p.straddress2,p.strcity,p.fk_intlocationid,p.strpostalcode,p.strhomephone,p.strbusinessphone,
 p.strmiscinfo1,p.strmiscinfo2,l.strsecretquestion,p.dteDateOfBirth,p.intgender,l.strsecretanswer
 from tblparticipants p inner join
 tblparticipantrights r on p.strindividualfk = r.strindividualfk inner join
 tblparticipantlogin l on p.strindividualfk = l.strindividualfk
 where p.fk_strsubgroupid = ''' +  @strsubgroupid + ''''

exec (@sql)

Error messages are:

Server: Msg 208, Level 16, State 1, Line 1
Invalid object name 'tblparticipants'.
Server: Msg 208, Level 16, State 1, Line 1
Invalid object name 'tblparticipantrights'.
Server: Msg 208, Level 16, State 1, Line 1
Invalid object name 'tblparticipantlogin'. 

Anyone see what may be the cause?

 thanks ^_^