Have you tried upgrading to the current version of the client software? (I think it’s 5.7 with 2 service packs) It may help – I have seen oddities with version 5.5.
There is no iSeries Access 5.5 nor 5.7 nor will there ever be. iSeries Access went from V5R1 to V5R2, V5R3, V5R4 to V6R1. Pcomm 5.5 was in either iSeries Access V5R1 or V5R2. Whichever is the correct version/release — V5R1 or V5R2 — you’ll want to verify that the latest service pack is on the PC.
Try the IBM i Access for Windows Service Packs web page.