Need advice (Informix 5.02)

Just a general query, we have been having some problems with our database/system/network and I want to know if anyone has seen or knows of problems like the ones we are having.... The database is used to store scanned images (10-20k each image and up to 40-50 images are scanned and then batched to the database to be updated) The hardware platform is a ALR 90Mhz Pentium system with 128M of memory, DPT disk controllers, 4 drives (striped). OS is Interactive Unix 3.01 NIC card is a 3Com 3C509b. Workstation front-end is a Powerbuilder application using ISTAR/INET client. Intermittantly users accessing/updating the database experience 6-8 minute response times when a transaction is updated (transmit screen and a new screen is displayed) or the application on the workstation hangs. Sometimes the Unix system itself runs very slow, when you look at sar it shows I/O activity going as high as 92% or user processes at 90%. Network streams resources show no failures. (Workstations are a mix of Win95 and Win3.1) Now please don't flame me.... I am just the poor network grunt who was brought in on these problems, the network is being blamed on all the problems.. What I'm after is...has anyone else seen anything like this?? any thoughts/ideas/troubleshooting tips would be greatly appreciated! Thanx for any help/ideas...... whitman@aottsd.uscourts.gov