Hey guys I am new to this party too... I just encountered this problem today and wanted to find solutions for that. But I haven't yet.
I would like to contribute some actions that I performed which might be clues to solving this problem:
1) I just installed msn (pecan) yesterday client for being online on my msn from my phone taking the toll to 1skype,1gtalk,1msn accounts to go on//offline every-time now.
2) Earlier I went to "Menu>Settings>Internet Connections>Connections>"My Home Wifi"& Edit>Next>Next>Next>Advanced>Other>and set the Wi-Fi Tx power to 10mW>Save" to save power as my phone was losing battery pretty fast as I wasn't used to that behaviour from my N5630XpMu...
3) Today I was talking on skype over wi-fi and I found that I was having a low quality talk. So I decided to change the power settings back to 100mW and "Power Saving" option to "On (Intermediate)".
This worked good marvels on my call quality (as my Wi-Fi source was in the adjacent house).
But later I started to find the Wi-Fi switcher problem...
It used to restart my phone whenever I chose to switch off the Wi-Fi.
But I noticed another interesting behaviour too:
It only does so when I switch it off and then try to press any other button as soon as I did that. (which I would do previously and it would be fine)
Usually I would press on the dialog which notifies "WLAN diabled". Even doing that now, created problems. So as a remedy, I waited for that dialog to disappear and I just observed that sometimes the problem doesn't persist but other times it does repeat itself...
Final Words: My suspect: msn (pecan) client or too many wifi sign offs before wi fi switch off...