Problem using API in VB.NET

Dears, (first, sorry for my bad english)

I’m using API in VB.NET and having problems with the comand:
/interface/wireless/monitor
=numbers=wlan1
=once=

in some servers and some interfaces have the error: Arithmetic Operation Resulted In An Overflow
in this line:
Case Is < &HC0
count = BitConverter.ToInt32(New Byte() {tcpStream.ReadByte(), tmp(3), 0, 0}, 0) ^ &H8000

testing this return, discover that return 1.#INF in this operation.

How resolve this ?

Thanks to advance.