updating table on different machine

Hi,
I use updates like this to keep data updated every night on certain tables across databases.

update A
set A.description = b.description,
A.shortdescription = b.shortdescription,
A.keywords = b.keywords,
A.smallimagepath = b.smallimagepath
from sfproducts A
join databaseb.dbo.sfproducts b on A.prodid = b.prodid
where A.description != b.description,
or A.shortdescription != b.shortdescription,
or A.keywords != b.keywords,
or A.smallimagepath != b.smallimagepath

The example above has 150,000+ rows and 170 columns.
Updating across databases on the same machine, it usually updates 5000 records a night in less than a minute.

We recently split the master tables off to another machine and the updates run for hours before I break them. Is this a limitation of sql server distributed transactions?
Any help would be greatly appreciated.
A linked server is being used and the servers are on the same internal network.

eric
this is my first post here, so let me know if you need more info.

could you guide me where to look for this ?

network packet size is 4096

database A supports ecommerce site with 200,000+ page views daily.
database B is central admin database where orders get fed into from the 3 frontend databases (1 of which is A in this case) and new product info gets fed out from to the 3 frontend databases. Database B supports 60 concurrent users inside here.

Also, I think I may have finally found the problem last night.
Updating distributed like this does not seem to like NTEXT fields.
1 of the major tables I was having problems with is working now.