Hi this is my first post

I have an application that takes data from remote sites every minute, that data is compressed and sent over a vpn where it is expanded on my main server.
I then have some vb code (written by others ) that deletes any duplications in the data, (i pull back two days worth of data each minute so there are duplications) this is step one in my sql job
step two imports the flat file into a SQL Databse
step three updates an analysis services cube
and finally the job is set to run every minute.

All works well but after a period (sometimes hours sometimes days the job hangs)
The log still shows the jobs running successfully but they have hung.

It's simple to get going again I stop the job and start it again and all is fine to the next hang

Can some one give me a steer as to how I can find out what is happening, please note I have been self taught sono to technical please
Many Thanks