Is that an IBM/Lenovo system and a ThinkPad with an Intel WiFi card ?
This was a big problem with ThinkPad's and lesser known notebook makers since it seems Lenovo had the audacity to tune their drivers up enough that SP3 broke it or just cause munginating frustration, other smaller boutique laptop makers modified their drivers for varied reasons but most often the noble reason of seeking peek performance and they also had to revise their drivers.
since Lenovo injects a slew of ThinkVantage branded software like other new PC bloatware, the tight integration of customization with generic SP3 revisions results in a war behind the scenes and the connection reliability suffers the most. If my speculation is correct, these specific links to Intelo pages offers patches and patched patches, the machine types may vary but the patches are often ubiquitous. Hopefully this helped or sets you towards the right direction.
) Update Intel® PROSet/Wireless WiFi Connection Utility (22.214.171.124)
using one of the following links:
(Multiple downloads for different Operating Systems)