There are a few probloms that can be causing frequent drop outs.
1. Diffraction/Refraction or scattering may be occuring. Diffraction is when the signal bends around and Refraction is when it bends though this will weaken the signal significantly. This will create a shadow of wireless conectivity that would cause frequent drop outs of the connection and very slow speeds. Scattering could happen but its unlikely in a household. I reccomend purchasing a WIFI compliant bi-directional amplifier and setting it in the middle of the machine and the AP.
2. Free Space Path Loss - Natural broadening of a signal of length, could be too long of a run, amp will work for this.
3. Dwell time could be exeeding 400 MS
You said other room, between walls is not healthy for a omnidirectional antenna, you want a good line of sight from the AP and the adaper on the machine in order for it to function right. Think of a antenna like an eye ball, you can see through some material but you cant others, you cant see through a dense wall and niether can an omni (not very well). Only highly directional antenn'a can beem though a wall.
Wireless is superb for buisness because in the office or class room, the line of sight for the AP's are very good, the AP has 3 modes, Root, Bridge and Repeater. Root is used for when the AP connects to a wired backbone, bridge and repeater is common sense. But wireless is never used byitself unless you have 2 machines that dont connect to the net. WEP security stops at the wired router, meaning in a big buisness your connection is just as secure as all wired with the exeption of people who war drive.
