Other Apps Dont Play Nice With .NET?

[scorpion53061]

I built a vb.net windows app for our customers that utilize our services.

This app uses Port 23(telnet) to communicate data to/from the user for order
entry and stock status as this form of communication works with my AIX
Server.

I also use SQL Server to record information of what the customer is looking
for (by the way the customers knows this and are ok with it - it is in the
agreement on which they agree to use the software. Often they like it
because if they get a price and dont buy it our salesman will call back with
a better price.)

The problem is that I have noticed that those customers running software
such as these the (my)application locks after it is open and in use for a
while:

Yahoo Messgenger(Most Reports), Kazza, Weatherbug, iMesh, AOL Instant
Messenger

Interestingly enough, MSN Messenger users do not have the (my)application
lock up on them. Those customers not having any of the above never
experience these issues. I have gotten reports of this occuring on all
platforms (98 - XP).

Has anyone have an idea of what might be going on here or have encountered a
similar problem?