Phill,

Some inline views may help simplify it:

select
    Account,
    Address1 = substring(address, 1, delimpos1-1),
    Address2 = substring(address, delimpos1+1, delimpos2-delimpos1-1),
    Address3 = substring(address, delimpos2+1, delimpos3-delimpos2-1),
    Address4 = substring(address, delimpos3+1, delimpos4-delimpos3-1),
    Address5 = substring(address, delimpos4+1, address_len-delimpos4)
from (
    select *, delimpos4=charindex(';', address, delimpos3+1)
    from (
        select *, delimpos3=charindex(';', address, delimpos2+1)
        from (
            select *, delimpos2=charindex(';', address, delimpos1+1)
            from (
                select *, address_len=len(address), delimpos1=charindex(';', address)
                from AddrSrc
            ) [Inline1]
        ) [Inline2]
    ) [Inline3]
) [Inline4]