Dropped WiFi connections can either be environmental or software related.
I'll try to keep this as generic as possible, so that the answer could apply to any WiFi cards.
Three environmental areas that you should consider before delving into the software suggestions below:
WIFI Encryption - Try changing the encryption method on your WIFI router, see if that results in a more stable connection.
WIFI Router itself - Try moving to a new access point, do you still have connectivity issues?
WIFI Channel - Try changing the channel your router is communicating on. In your area, there may be too much traffic on the channel you selected.
Once you've ruled these areas out, five software possible avenues you could consider:
- Looking to see if any WiFi Backport exist and if so, installing the appropriate package
- See if this is a 64bit vs 32bit issue
- Trying a newer Kernel, either the next available stable kernel OR testing the very latest alpha/beta Ubuntu version which contains the latest release candidate kernel
- Disabling the power management of your wireless card
- (the choice of very last resort) using NDISWrapper
The kernel developers often release a software package containing updates for WiFi devices derived from the latest or most recent kernel.
For Natty, this package is called
linux-backports-modules-cw-2.6.39-generic (thanks Jorge). This package can be found either in the proposed repository or in the backport repository. Tick the appropriate checkbox in Software Sources and Reload the latest updates.
Open either Software Center or Synaptic Manager and search for the package named (or similarly named) as above. If the package is available, install the package, reboot and see if the WiFi connection is more stable.
64bit vs 32bit
As linux matures, 64bit vs 32bits issues should reduce. However it is not unknown that a 64bit installation can be more unstable compared to a 32bit installation - and visa-versa.
For your card, I found a bug report for your Wireless card here that describes your symptoms - 64bit kernel, wifi drops connection randomly.
Take a backup of your system first using, for example, Clonezilla, so that you have something you can easily restore from.
Try installing the 32bit version of Natty. See if your connection is more stable. You could also test the other suggestions in this answer in this 32bit configuration.
Testing a newer Kernel can sometimes cause instability issues - for example boot and black-screen issues. I would recommend you remove any Additional Hardware graphic drivers (e.g. ATI or Nvidia) first. I also recommend that you have a good backup for example, using CloneZilla which you can restore from.
Look for the next stable mainline kernel from here on LaunchPad.
Looking at the change lists on kernel 2.6.39, it does mention some updates for your card.
You can install the 2.6.39 kernel as described in my answer here.
Disabling Power Management
Sometimes wireless cards can have Power Management modes. Its not unknown for these modes to be buggy in linux. Switching off power-management can sometimes help.
You may have to do some Google research to see if there is a specific method to disable Power Managment. Below is a method I've used in the past for some cards.
From a terminal type:
gksu gedit /etc/pm/power.d/wireless
If the file opened contains any statements then add the following line (if it doesnt already exist)
/sbin/iwconfig wlan0 power off
If the file opened is empty then add the following
/sbin/iwconfig wlan0 power off
Now copy and paste the following:
sudo chmod +x /etc/pm/power.d/wireless
Note - NDISWrapper can cause black-screen issues on boot - so have a good backup for example, using CloneZilla which you can restore from.
NDISWrapper was at one time a few years ago, one frequently used method for wireless cards because the kernel had so few wireless driver support.
Its fallen out of favour in recent times for many reasons that I wont go into...
To be honest, RTL8187se has been in the kernel for some time so the following suggestion should be considered as a last resort.
ndisgtk in the software center and install
Now download the windows xp drivers, in your case from Realtek
Extract from the zip file.
Using ndisgtk - navigate to the folder - RTL8187SE - WinXP and point ndisgtk to the
.inf file. Hopefully now (maybe after a reboot) network manager should use this driver in preference to the RTL8187SE kernel driver - n.b. hopefully you dont have to blacklist the kernel.