I noticed this as well too. it doesn't seem to happen all the time but it has happened to me on occasion.

 

This mostly has happened to me when I hit the "downloads" button. It can take more than five tries sometimes, other times I get it on the first try.

 

I have had to turn off wifi to get to the markets downloads.

 

I as well can get into the market fine, but must turn off wifi to download. I've also had wifi interfere with installing a couple things like MyVerizon and Wavesecure.

 

I've only encountered this problem if I open the Market and realize my WiFi is not on, back out, turn it on, get back into the market and it fail to open. But, if I already have WiFi on, signal found and connected... I have no problem opening Market and doing all my downloads.

 

This has recently started happening to me. I used iptables on my router to log all traffic from my phone while I started the market app with the wifi on. Nothing, not a single packet originated from my phone from the time I started market until the time I got the network error. Alternatively, using the browser logs a ton of packets. I hope someone from Google reads this because the issue lies in their code, and it is really starting to piss me off...