Hi Dmitry,
checking the replies you got so far, here are my two cents:

If there would be such a problem with the network, guess your customers would notice it in other operations. With ANY index your query should be practically instantanous with this 'ridiculos' 150k records.

You did not say if you´re querying in Fox or against a server. I´ll try the inner workings of Fox later and tell the tip (which applies to SQL Server):
Depending on the settings, if you got an uncommitted, long running transaction / lock(s) from one user, the query of a different user might wait until commit / unlock. (Hopefully you don´t have user-interaction amidst a transaction!)

With the SELECT there are several options to execute the query, no matter what the locks are. Dunno the exact syntax off the top of my head, but they are READ_PAST, READ COMMITTED or READ UNCOMMITTED.

In a nutshell. Think it´s a locking problem.
Hope this helps.
G