Wireless might still be regarded as a convenience rather than a solid networking technique -- though I rely upon it 24/7 and at the limits of reliable reception thru two walls and down one floor (total distance about 35 feet). It generally works remarkably well given that I live in an area of offices and studio apartments of which perhaps half have wireless.
As for your issue -- look at reception and interference.
Is there a new network nearby ? Have you selected the optimum channel for your environment ? The different frequencies work better or worse in different environments. You should select a channel which is five stops from any strong neighbouring network.
Do you or a close neighbour have cordless phones, cordless baby alarm etc.
Performance is intimately linked to your environment, the actual equipment used and the settings on that equipment. Plus the multifold variations possible within Windows (and various versions thereof). So it's virtually impossible to come up with a definitive answer to your issue. You'll have to experiment.
You might also explain in more detail what your wireless setu is and any symptoms and what steps you have tried.
The lack of responses to your original post may simply be because you tried to explain the issue in the heading and ran out of space.