SQL Server : datetime incorrect results -

using sql server 2008,

i have procedure follows:

select      userid, name, company, languageid, coderegisteredwith, totalloggedinduration,      region, isadmin,     isrep, isretailer, isteamleader, [dateregistered]       roundupacademy.dbo.userprofile with(nolock)      (convert(smalldatetime, dateregistered, 120) >= convert(smalldatetime, '2013-1-1', 120)      , (convert(smalldatetime, dateregistered, 120) <= convert(smalldatetime, '2013-8-8', 120))) 

this works fine , shows results between dates.

however when expanding on query , more conditions follows:

select     userid, name, company, languageid, coderegisteredwith, totalloggedinduration,         region, isadmin, isrep, isretailer, isteamleader, [dateregistered]      roundupacademy.dbo.userprofile with(nolock)     userid not null or userid not ''     ,     (@languageid = 0 or ([languageid] = @languageid ))    ,     ((convert(smalldatetime, dateregistered, 120) >= convert(smalldatetime, @datereg,  120)  , (convert(smalldatetime, dateregistered, 120) <= convert(smalldatetime, @dateend, 120)))) 

it seems date shows.

not sure problem other conditions fine.

any ideas?

replace

where userid not null or userid not ''  

with

where (userid not null or userid not '') 

otherwise records userid not null or other conditions true.