If you suddenly find your internet connection down with SonicWall it's probably because a power surge reset the modem to factory settings. This means that the modem supplies the PPPoE information NOT the SonicWall. You want the SonicWall to handle everything and need to put the modem in "Bridged" mode.

If you use a SonicWALL SonicPoint N wireless access point, you may find that while Windows and Android users have no problems connecting to your wireless, iPhone and iPad users can’t get on.  They can see the wireless network and appear to connect to it, but they actually never get an IP address and consequently will be stuck.

SonicWall doesn't want you to access your LAN via a SonicPoint wireless access point, but they don't tell you that. You might be expecting to be able to access your LAN after you've connected and set up your SonicPoint-- but think again. Even though you can reach the Internet, you'll discover that LAN access is elusive. Configuring access rules and Zones and Guest Services doesn't help.  Apparently the way SonicWalls are designed to operate is to allow Internet Access, but to deny LAN access. Anyone who wants LAN access via internal wireless will have to use a VPN.  This can be a real pain, but is definately more secure. 

We found that our sonicwall would cause all downloads to start very fast, slow down quickly, and eventually stop.  This occurred with major corporate download sites.  The download went to low KB/s before dying.  A download time estimate would indicate hours and days remaining.